5.0 × 10–4 M solution in toluene, 2.0 × 10–4 mmol for both PF-G2 andWPF-G2R3), monomer R (0.60 mL 5.0 × 10–4 M solution in toluene,3.0 × 10–4 mmol for both PF-R3 and WPF-G2R3), N-methyl-N,N-dioctyl-1-octanaminium chloride (Aliquat 336; 0.10 g, 0.25 mmol),and tetrakis(triphenylphosphine)palladium (11.0 mg, 0.01 mmol) un-der argon was added 2 mL 2 M aqueous potassium carbonate and6 mL toluene. The mixture was stirred at 90 °C for 48 h and thenpoured into methanol. The precipitate was collected by filtration,dried, and then dissolved in dichloromethane. The solution waswashed with water and dried over anhydrous Na2SO4. After most ofthe solvent had been removed, the residue was poured into stirredmethanol to give a fiber-like solid. The polymer was further purifiedby extraction with acetone for 24 h. The reprecipitation procedurewith dichloromethane/methanol was then repeated several times. Thefinal product, a light-yellow or light-pink fiber, was obtained after dry-ing in vacuum with a yield of 45–60 %. PF, PF-G2, PF-R3, and WPF-G2R3 all showed similar 1H NMR spectra and elemental analyses. Forexample, WPF-G2R3: 1H NMR (300 MHz, CDCl3, d): 7.87 (d, 2H),7.72 (br, 4H), 2.10 (br, 4H), 1.14 (br, 24H), 0.81 (t, 6H). Anal. Calcdfor C29 H40: C, 89.69; H, 10.31. Found: C, 89.08; H, 10.02. The contentof DPAN and TPATBT units in these polymers was too low to be de-tected by 1H NMR and elemental analysis. We found that, when thefeed ratio of the monomers G and R was as high as 5 mol-%, the ac-tual content of DPAN or TPATBT in the resulting polymers calcu-lated by 1H NMR was 3.8 mol-% and 4.1 mol-%, respectively, whichwas similar to the feed ratio of the monomers. Therefore, we assumedthat the actual content of DPAN or TPATBT in PF-G2, PF-R3, andWPF-G2R3 was the same as the feed ratio of the correspondingmonomers.

Received: September 2, 2005Final version: September 26, 2005

Published online: November 3, 2005–

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DOI: 10.1002/adma.200500544

Exploiting Length Scales of Exchange-Bias Systems to Fully TailorDouble-Shifted Hysteresis Loops**

By Sebastian Brück, Jordi Sort,* Vincent Baltz,Santiago Suriñach, Juan Santiago Muñoz,Bernard Dieny, Maria Dolors Baró, and Josep Nogués

The shapes of magnetic hysteresis loops is usually ascribedto internal material parameters (e.g., grain size or strain).Thus, magnetic properties typically remain fixed after samplepreparation. However, tailoring the loop shape by using post-deposition external parameters is very appealing from a tech-nological point of view. We demonstrate the possibility of en-gineering fully adjustable double-shifted hysteresis loops in aferromagnetic–antiferromagnetic system exhibiting a mag-

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–[*] Dr. J. Sort, Prof. J. Nogués

Institució Catalana de Recerca i Estudis Avançats (ICREA) andDepartment de Física Universitat Autònoma de BarcelonaES-08193 Bellaterra (Spain)E-mail: jordi.sort@uab.esS. Brück, Prof. S. Suriñach, Prof. J. S. Muñoz, Prof. M. D. BaróDepartament de Física, Universitat Autònoma de BarcelonaES-08193 Bellaterra (Spain)V. Baltz, Prof. B. DienySPINTEC (URA 2512), CEA/CNRS17 Av. Martyrs, F-38054 Grenoble Cedex 9 (France)

[**] The authors thank A. Hoffmann for useful discussions. Financialsupport from the NEXBIAS (HPRN-CT 2002-00296), the 2001-SGR-00189, and the MAT-2004-01679 research projects is acknowledged.

netic anisotropy perpendicular to the plane. It is shown thatboth the magnetization amplitude and the loop shift of eachof the two sub-loops composing the dual loop can be indepen-dently tailored, allowing the whole loop to be tuned from asymmetric double-shifted to a single-shifted hysteresis loop.The precise manipulation of the diverse parameters of eachindividual loop is accomplished by the interplay between themagnetic lateral length scales of the antiferromagnetic andferromagnetic magnetic structures arising from different typesof cooling procedures.

Bilayer systems consisting of a ferromagnet (F) exchangecoupled to an antiferromagnet (AF) typically exhibit a shift ofthe hysteresis loop along the magnetic-field axis when theyare field-cooled from above the Néel temperature of the AF,TN. Note that the temperature at which this shift vanishes, i.e.,the blocking temperature TB, is usually lower than TN. Theloop shift, referred to as the exchange-bias field, HE, is relatedto a F–AF exchange coupling interaction across the interfaceand is usually accompanied by an increase of the F coercivity,HC.

[1–4] Although this phenomenon has been extensively stud-ied, mainly due to its relevance in spin valves or magnetic tun-nel junction applications,[5–7] the microscopic mechanismsleading to exchange bias are not fully understood. Neverthe-less, so far many of the existing theoretical models explain theobserved behavior by the formation and pinning of domainseither in the F[8,9] or in the AF.[10–12] Although the majority ofexchange-bias systems are bilayers with an in-plane magneticanisotropy,[1–4] in recent years it has been shown that ex-change bias can also be induced perpendicular to the plane inmultilayers exhibiting a perpendicular magnetic anisotro-py.[13–17]

An interesting feature observed in some in-plane exchange-bias systems is the occurrence of double-shifted hysteresisloops. Under certain conditions, rather than exhibiting a sin-gle-shifted hysteresis loop, these systems exhibit a loop that isdivided into two sub-loops, one shifted to positive fields andthe other to negative fields. This effect is usually observedwhen the F–AF system is either zero-field cooled in a demag-netized state, cooled in large fields, or grown in zerofield.[18–24] The dual loops appear to originate from an imprintof the domain pattern of the F into the AF during the coolingprocedure. If the F system exhibits an uniaxial anisotropyabove TB, when it is demagnetized, it evolves into magneticdomains of opposite magnetization direction along the easyaxis. The imprint of such domain structure of the F onto theAF during the zero-field cooling (ZFC) procedure divides theAF into two types of regions locally oriented in opposite di-rections. Note that these regions are not necessarily AF do-mains in the strict thermodynamic sense, but rather are areaswhere the properties of the AF, most likely the orientation ofthe AF uncompensated spins, have been modified due to thepresence of the F. When a hysteresis loop is carried out belowTB, each of these AF regions couples in opposite ways to theF, hence resulting in one sub-loop shifted towards the posi-tive-field axis and another shifted towards the negative direc-tion. It has been shown that, for in-plane systems, the vertical

amplitude of the dual-loops depends on the magnetizationstate of the F above TB.[18,20,23] However, an actual tailoring ofboth the magnetization amplitude and the loop shift of the in-dividual sub-loops has yet been achieved neither for in-planenor for out-of-plane systems.

In this communication, we show that double-shifted loops inF–AF systems with out-of-plane anisotropy can be easily ob-tained and fully tuned. The system is composed of a single F[Pt/Co] multilayer exchange coupled to an AF IrMn layer.Once the dual loop is set, both the amplitude and the loopshift of each sub-loop can be separately controlled by appro-priate cooling procedures. Such independent tailoring of theloops is possible by exploiting the difference in “domain sizes”between the AF and F, depending on the cooling procedure.

The hysteresis loop after the ZFC process from a demagne-tized state, i.e., from a remanence MR = 0, is shown in Figure 1a.

It can be seen that the system exhibits a double-shifted loopconsisting of one sub-loop shifted towards the negative fieldaxis and the other towards positive fields, both with nearly thesame vertical magnetization amplitude, DM, the same abso-lute value of the loop shift, l0HE ∼ 24 mT, and the samecoercivity, l0HC ∼ 32 mT (l0: magnetic permeability of freespace). The appearance of the dual loop indicates that themagnetic structure in the AF has been subdivided into twotypes of regions which couple to the F in opposite direc-tions.[18–23] The formation of such a magnetic structure of theAF has been ascribed, for in-plane systems, to an imprint ofthe F domain pattern into the AF during the cooling.[25,26] Inthe particular case of [Pt/Co] multilayers with out-of-planeanisotropy, due to their well-defined uniaxial anisotropy,[27,28]

a maze domain structure (consisting of up and down domains)forms when the system is alternating current (AC)-demagne-tized out-of-plane.[29] For a completely demagnetized state inthe F, since MR = 0, an equal proportion of up and down mag-netization regions exists. Thus, when the F domain structure isimprinted to the AF during the cooling, equal areas of AFwith opposite magnetic structure are created. This balancedAF magnetic structure results in a fully symmetric double-shifted hysteresis loop. It is noteworthy that this reasoning im-plies that during magnetization reversal the imprinted regionsof AF with opposite magnetic structure have to be similar insize, or eventually larger, than the domains in the F. If the Fdomains were much larger than the AF-imprinted regions,then each F domain would feel the average effect of severalof these AF regions, leading to the disappearance of the dual-shifted loops.[23]

To induce dual loops with variable magnetization ampli-tude, a procedure based on cooling in different magnetizationstates from a temperature TDem, which lies above the maxi-mum blocking temperature of the AF, has been utilized.[18,23]

At TDem = 520 K, after AC-demagnetization, a small field(smaller than the field necessary to saturate the sample) is ap-plied and subsequently removed. This minor loop procedurecreates a remanent state in the F characterized by a non-zero MR. By applying different maximum fields (in therange 0 < l0HMax < 800 mT), remanent states in the range

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0 < MR < MS (where MS is the saturation magnetization) canbe obtained. Once the remanent state is set (at TDem = 520 K),the sample is zero-field cooled to room temperature. The re-sulting loops are shown in Figure 1 (b1–b4) for remanent-to-saturation magnetization ratios of MR/MS = 0.22 (Fig. 1 (b1)),MR/MS = 0.43 (Fig. 1 (b2)), MR/MS = 0.73 (Fig. 1 (b3)), andMR/MS = 0.93 (Fig. 1 (b4)), respectively. The loops reveal thatfor increasing MR/MS ratios, the exchange bias HE of the twosub-loops remains constant, whereas the magnetization ampli-tude progressively changes. As MR/MS increases, the sub-loopshifted towards positive fields, in the following referred to asthe HE

+ sub-loop (see Fig. 1a), decreases in amplitude whilethe one shifted towards negative fields, i.e., the HE

– sub-loop,correlatively increases. This procedure allows the tuning ofthe whole system from a symmetric dual-loop towards ashifted single-loop. To better illustrate this tuning, plotted inFigure 2 is the dependence of the normalized magnetizationamplitude of the HE

– sub-loop, DM, versus the MR/MS ratio.

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Figure 1. Magnetic-hysteresis loops measured along the perpendicular to the plane, showing both ways of tuning the F–AF system. The upper curve in(a) is the room-temperature (RT) hysteresis loop after ZFC the alternating current-demagnetized sample from 520 K. The loop shift of the left loop,HE

–, the right loop, HE+, and the magnetization amplitude, DM, are defined in the Figure. The left column (b) shows the tuning of the vertical ampli-

tude of the system: room-temperature hysteresis loops after ZFC from a demagnetization temperature TDem = 520 K in a state with MR/MS = 0.22 (b1),MR/MS = 0.43 (b2), MR/MS = 0.73 (b3), and MR/MS = 0.93 (b4); MS: saturation magnetization. The arrows highlight the evolution of the magnetizationamplitude with M

R/MS. On the right-hand plots (c) the horizontal tailoring of the system is displayed: RT hysteresis loops after ZFC from a MR/MS = 0

state and subsequently field cooling in l0H = 800 mT (l0: magnetic permeability of free space) from different annealing temperature (TANN) values;TANN = 350 K (c1), TANN = 370 K (c2), TANN = 390 K (c3), and TANN = 520 K (c4). The line emphasizes the evolution of HE with TANN. Schematic dia-grams describing the cooling procedures used for the vertical and horizontal tuning of the double-shifted loops are shown at the left and right parts ofthe figure, respectively.

Figure 2. Dependence of the normalized magnetization amplitude of thesub-loop shifted towards the negative fields, DM, versus the MR/MS ra-tio. The different insets show the corresponding magnetic-force micros-copy images for a) MR/MS = 0, b) MR/MS = 0.43, and c) MR/MS = 0.93.Note that each image has a side length of 20 lm.

It can be seen that DM increases almost linearly withMR/MS. To understand this correlation, the magnetic-domainconfigurations in the F, after the successive ZFC process fromdifferent remanent states, were studied by magnetic-forcemicroscopy (MFM). The recorded MFM images shown inFigure 2 are the ones corresponding to MR/MS = 0.0,MR/MS = 0.43, and MR/MS = 0.93. As expected, a balance be-tween up and down domains (dark versus bright areas) in theF is observed for the zero-field-cooled, fully demagnetized,sample, i.e., MR = 0. As MR/MS increases, the bright areas ex-pand at the expense of the darker ones. For example, in thecase of MR/MS = 0.43 the up domains cover 66 % of the image,while for MR/MS = 0.93 the MFM image shows virtually nodomain pattern, indicating that the sample is almost saturat-ed. The relative areas covered by bright and dark regionsfound from the MFM images are in good agreement with thepercentage increase of the amplitude DM of the HE

– sub-loopas shown in Figure 2. This confirms that the imprinted AFmagnetic structures actually mimic the F domain structure,where the AF areas with one orientation decrease at the ex-pense of the areas with opposite orientation.

From a practical point of view, it would be desirable notonly to be able to tune the vertical amplitude, but also to in-dependently shift, horizontally, each of the two sub-loopscomposing the dual loop. To achieve this, the exchange cou-pling has to be altered by means of a second cooling proce-dure. The initial step is the standard full demagnetization atTDem = 520 K and ZFC to room temperature, which renders asymmetrical double-shifted hysteresis loop (Fig. 1a). Subse-quently the sample is heated again, although now to a temper-ature, TANN, lower than the maximum blocking temperature(which is below 520 K). The sample is then field cooled fromTANN to room temperature in a field l0HFC = 800 mT, whichis sufficient to saturate the F layer. To achieve different valuesof HE for one of the sub-loops, the process is repeated for dif-ferent TANN values in the range 300 K < TANN < 390 K. Fig-ures 1 (c1–3) show the resulting hysteresis loopsafter field cooling from TANN = 350, 370, and390 K, respectively. As can be seen, a tailoring ofthe horizontal shift, evidenced by the change of HE

of the HE+ sub-loop, can indeed be accomplished

by this two-step cooling procedure. Interestingly, itcan be seen that while the magnitude of HE

+ de-creases smoothly with TANN, HE

– remains constant.Moreover, DM of both sub-loops remains un-changed. Hence, the system is tailored again froma symmetric dual loop to a single-shifted loop, al-though this time by varying HE of one of the sub-loops, rather than changing DM as in the previouscase.

To understand this second type of cooling proce-dure, one has to take into account the existence ofa distribution of blocking temperatures, TB.[30] Thedistribution in TB stems from the distribution ofcrystallite sizes, stoichiometry, strains, or defects inthe layer. This means that, locally, some areas lose

HE at different temperatures than others. This is illustrated inthe top-right panel of Figure 3 for [Co/Pt]/IrMn, which showsthe blocking temperature distribution of the system obtainedby differentiating the TANN dependence of HE. If the systemis warmed to a temperature TANN below the maximum TB,the magnetic order of the AF particles in the hatched area ofthe distribution (Fig. 3) becomes thermally unstable, whereasthe spin lattice of the AF particles in the white area remainsunchanged.

After ZFC from a demagnetized state, the initial state ofthe AF, as shown in Figure 3a, is an imprint of the domainpattern of the F, i.e., the AF areas with interfacial uncompen-sated moment in the opposite directions are equal. If the sam-ple is then heated to, e.g., TANN = 350 K, some AF regionswith local TB lower than 350 K (marked in gray in Fig. 3a)will be thermally unstable (i.e., they start to behave like asuperparamagnet exposed to the applied field) at this temper-ature. If a strong external field is applied at this temperatureso that the F becomes saturated, the AF regions with low localTB will then reorient during the subsequent cooling accordingto the direction of the external field (Fig. 3b). However, sincethe state of the AF is composed of “up and down” magneticstructures, only the local areas of imprinted AF regions withan antiparallel orientation with respect to the external fieldwill create local “antiparallel domains” within the AF im-printed region, as shown in the dotted area of Figure 3b. Con-versely, the imprinted regions where the net AF magneticstructure is parallel to the cooling field will remain unchangedsince, even though they were demagnetized locally at TANN,during the field cooling they will be remagnetized along thesame original direction (the hatched area in Fig. 3b). The factthat local AF antiparallel structures are created only in one ofthe imprinted AF areas explains why only one of the sub-loops (in this case, HE

+) is altered by the second thermal pro-cess. Moreover, these local regions can be argued to be eitherof the size of the AF grain size (typically 10 nm) or the AF

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Figure 3. Sketch of the magnetic configurations in the system after each cooling stepaccording to the explanation given in the text. The inset shows the blocking tempera-ture distribution of the system derived from calculating the derivative of the evolutionof HE with TANN.

domain size (dAF ∼ 160 nm[31]). In any case, they are muchsmaller than the F domain width, which, as seen in Figure 2, isof the order of 1–2 lm. Consequently, the effects of these lo-cal AF structures are averaged over each F domain. Thus, if20 % of the imprinted area has reversed local structures, thenet effect will be as if the average interface coupling of thisimprinted area had been reduced by 20 %. This averaging ef-fect clarifies why, in this case, the thermal treatment controlsHE, rather than DM, of one of the sub-loop. By increasingTANN, the number of locally reversed AF structures increases.Since an increasing number of local areas within the AF be-come superparamagnetic for higher TANN, the average inter-face coupling reduces and consequently HE decreases. Notethat due to the origin of the distribution of blocking tempera-tures, this “horizontal” tuning may be more effective for poly-crystalline systems.

From the two above engineering procedures, it is notewor-thy that when the ratio of F domain size to AF “domain size”DF/DAF ∼ 1, i.e., when the AF “domains” are of similar sizethan the F domains, the magnetization amplitude is tailored(Fig. 1b). However when DF/DAF > 1, i.e., the AF “domains”are smaller than those of the F, the loop shift of the individualsub-loops can be controlled (Fig. 1c). These effects clearlydemonstrate the importance of the interplay between themagnetic lateral length scales of the AF and F domains forexchange-bias phenomena. Note also that out-of-plane anisot-ropy is not essential to observe the described phenomena.However, the well-defined uniaxial anisotropy and domainstructure of the F in our system make the effects more pro-nounced.

The processes that control the dual loops can actually be com-bined to fully tailor a hysteresis-loop shape. Two examples aregiven in Figure 4, where i) one loop with increased DM (withrespect to the AC-demagnetized sample, Fig. 1a) and reducedHE

+ (with unaffected HE–) and ii) one loop with increased DM

and reduced HE– (with unaffected HE

+) are presented.For case (i), the sample was first zero-field cooled from 520 K

to room temperature with MR/MS = 0.43 and subsequentlyfield cooled again from TANN = 360 K in l0HFC = +800 mT. Incase (ii), the sample was first zero-field cooled from 520 K, also

with MR/MS = 0.43, and then field cooled from TANN = 360 K inl0HFC = –800 mT. Note the change of sign of the cooling fieldfor the second cooling process. Similarly, if the sign of MR/MS ischanged before the ZFC, DM of the HE

– sub-loop would besmaller, instead of larger, than DM of the HE

+ sub-loop. There-fore, more complex hysteresis loops can be devised by carefullydesigning the thermal treatment of the samples.

Finally, note that controlling the hysteresis loop of magneticmaterials by using post-deposition, extrinsic parameters (e.g.,field cooling using different procedures) is appealing since itmay allow controlling the magnetic properties to match specif-ic purposes. In particular, tailoring the shape of dual loops maybe interesting for novel types of magnetoelectronic devices.

In summary, we have shown that it is possible to engineerdouble-shifted loops with fully adjustable shapes in a systemwith anisotropy perpendicular to the plane composed of a sin-gle F multilayer exchange coupled to an AF. The mechanismresponsible for the formation of such dual loops can be as-cribed to an imprinting of the domain pattern of the F into theAF during ZFC through the AF blocking temperature. Thetailoring of the loop shapes can be carried out by taking ad-vantage of the interplay between different magnetic lengthscales involved in the exchange-bias phenomena. By ZFC thesamples in different remanent states (i.e., different F domainconfigurations), it is possible to tailor the vertical amplitudeof each sub-loop composing the dual loop. Furthermore, bycarrying out a ZFC process followed by FC processes fromdifferent, lower, temperatures, the exchange-bias fields ofeach of the sub-loops can be controllably and independentlytuned, allowing the loop shape to vary from single- to double-shifted hysteresis loops, providing a valuable tool to engineerthe magnetic properties, i.e., hysteresis loops, of [Pt/Co] multi-layers after they have been deposited.

Experimental

The system investigated here consisted of a ferromagnetic multi-layer (ML) coupled to an antiferromagnetic layer. The exact structurewas composed of [Pt(2 nm)/Co(0.65 nm)]3/Pt(0.1 nm)/IrMn(5 nm)/Pt(2 nm), which was deposited onto a thermally oxidized Si wafer bydirect-current magnetron sputtering. Note that Pt/Co MLs of thisthickness ratio exhibit a well-pronounced magnetic perpendicular an-isotropy. The deposition took place at room temperature and underan argon pressure of 0.25 Pa, after having reached a base pressure of5.3 × 10–6 Pa. It should be noted that an ultrathin Pt spacer was intro-duced between the last Co layer in the ML and the IrMn because itwas shown to largely enhance the exchange-bias strength [17]. Afterpreparation, the sample was heated to TDem = 520 K (20 min), whichlies above the blocking temperature distribution of the AF (as can beseen in the inset of Figure 3, the average blocking temperature isaround 380 K, while the maximum blocking temperature is slightlybelow 520 K; note that the Néel temperature of the AF is aboutTN ∼ 690 K [1]) and was demagnetized by applying an alternatingfield of decreasing amplitude perpendicular to the plane. To inducedouble-shifted loops, the samples were zero-field cooled fromTDem = 520 K to room temperature. For the magnetization tailoring,the system was zero-field cooled after creating different remanentstates at TDem. The loop-shift tuning was induced by heating the sam-ple in a dual-loop state to TANN < TB for 20 min and subsequentlyfield cooling (l0HFC = 800 mT) it to room temperature. The hysteresis

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Figure 4. Magnetic hysteresis loops showing full tailoring of the dualloop. Displayed in (i) is the loop after ZFC from 520 K in a state withMR/MS = 0.43 (�), as in Figure 1 (b2), and after the subsequent fieldcooling from TANN = 360 K in l0HFC = +800 mT (�). In (ii), the same pro-cedure but with l0HFC = –800 mT is shown (following the same nota-tion).

loops were measured at room temperature using a vibrating samplemagnetometer (VSM) with the external field being applied perpen-dicular to the plane. The magnetic domain structure of the F was im-aged by magnetic-force microscopy (MFM) immediately after theZFC procedure, prior to the application of any external field.

Received: March 15, 2005Final version: August 4, 2005

Published online: November 3, 2005

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DOI: 10.1002/adma.200501492

Metallodielectric Two-DimensionalPhotonic Structures Madeby Electric-Field Microstructuringof Nanocomposite Glasses**

By Amin Abdolvand, Alexander Podlipensky,Sven Matthias, Frank Syrowatka, Ulrich Gösele,Gerhard Seifert, and Heinrich Graener*

Dielectrics containing metallic nanoparticles constitute apromising class of materials for various photonics applicationsdue to their unique linear and nonlinear optical properties,which result mainly from the strong surface plasmon resonan-ces (SPR) of the metallic inclusions. Since these resonancescan be varied within a wide spectral range throughout the visi-ble and near infrared by choice of the metal and dielectricmatrix as well as by manipulation of size, shape, and spatialdistribution of the metal clusters,[1–5] such materials allow flex-ible engineering of their optical properties. In particular,metallodielectric photonic crystals have recently been pro-posed as possible candidates for achieving a photonic bandgapin the visible-wavelength range.[6,7] However, productionof optical micro- and nanostructures in metallodielectricsrequires gaining control over the above-mentioned parame-ters of the metallic inclusions. Established elaborate tech-niques like electron-beam lithography or those that involvelasers, while proven to be powerful and flexible tools for thispurpose,[8–11] are often costly and/or time-consuming.

In this work, we demonstrate a comparatively simple tech-nique to prepare large-area, regular photonic micro- andnanostructures in silver-doped nanocomposite glass by modi-fying the spatial distribution of the nanoparticles with a directcurrent (DC) electric field. The technique exploits the veryrecently reported effect of “electric-field-assisted dissolution”(EFAD) of metallic nanoparticles:[12,13] silver nanoparticlesembedded in a glass matrix can be destroyed and dissolved inthe glass in the form of Ag+ ions by a combination of anintense DC electric field (∼ 1 kV) and moderately elevatedtemperature (∼ 280 °C). This process can lead to total trans-

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Adv. Mater. 2005, 17, 2983–2987 © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 2983

–[*] Prof. H. Graener, A. Abdolvand, Dr. A. Podlipensky, Dr. G. Seifert

Physics Department, Martin-Luther-UniversityHoher Weg 8, D-06120 Halle (Germany)E-mail: graener@physik.uni-halle.deDr. S. Matthias, Prof. U. GöseleMax Planck Institute of Microstructure PhysicsWeinberg 2, D-06120 Halle (Germany)F. SyrowatkaIWZ Materialwissenschaft, Martin-Luther-UniversityHoher Weg 8, D-06120 Halle (Germany)

[**] The authors are very grateful to CODIXX AG at Barleben/Germanyfor providing the samples for this study.