Magnetoresistive Random Access Memory (MRAM)

Vimal Kumar Shukla

2451-13-744-030ME VLES

DEPARTMENT OF ECE

OUTLINE :IntroductionMagnetic Core RAMMRAM

Fixed LayerReading ProcessWriting ProcessCharacteristics

Other RAM TechnologiesMRAM Vs Other RAM TechnologiesFuture MRAM ImprovementsApplicationsReferences

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Introduction

•Why can’t your pc simply turn on like your television?

•MRAM uses magnetism rather than electrical power to store bits of data.•No refresh is needed to retain the data.•For users of laptops and other mobile devices, such as MP3 players and cell phones, MRAM is the holy grail of longer battery life.

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Magnetic Core RAM

By the early 1960’s, Magnetic Core RAM became largely universal as main memory, replacing drum memory

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Magnetic Core RAM

• The memory cells consist of wired threaded tiny ferrite rings (cores).

• X and Y lines to apply the magnetic filed.

• Sense/Inhibit line to ‘read’ the current pulse when the polarization of the magnetic field changes.

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Magnetic Tunnel Junction (MTJ)

Commonly used insulating materials are Aluminum oxide (Al2O3) and crystalline Magnesium oxide (MgO)

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MRAM

One of the two plates is a permanent magnet set to a particular polarity, the other's field will change to match that of an external field.

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MRAM: Fixed layer

The bottom layers give an effect of fixed (pinned) layer due to interlayer exchange coupling between ferromagnetic and spacer layer of synthetic antiferromagnetic.

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MRAM: Reading process

• Transistor is “ON”

• Measuring of electrical resistance of a small sense current from a supply line through the cell to the ground.

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MRAM: Writing process

• Transistor is “OFF” 

• When current is passed through the write lines, an induced magnetic field is created at the junction, which alters the polarity of the free layer.

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MRAM: Writing process

• In order to change the polarity of the free layer, both fields are necessary.

• Only the bit in which current is applied in both hard and easy axis will be written. The other bits will remain half-select.

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MRAM: Characteristics

• Non-volatility

• Infinite endurance

• High speed performance

• Low cost

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Other RAM Technologies

Each bit of data is stored in a separate capacitor within an integrated circuitCharacteristics• Volatile• The highest density RAM currently available• The least expensive one• Moderately fast

DRAM

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Other RAM Technologies

Each bit is stored on four transistors that form two cross-coupled inverters

Characteristics• Expensive• Volatile• Fast• Low power consumption• Less dense than DRAM

SRAM

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Other RAM Technologies

Flash RAMStores information in an array of memory cells made from floating-gate transistorsCharacteristics• Cheap• Non-volatile• Slow• Enormously durable• Limited endurance

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MRAM Vs Other RAM TechnologiesM.V.S.R.E.C

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MRAM Vs Other RAM Technologies

MRAM combines the best characteristics of DRAM, SRAM and Flash RAM

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Future MRAM Improvements

Thermal Assisted Switching

• Solves the first-generation selectivity and stability problems

• Cost-effective and scalable memory technology to at least the 32nm node

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Future MRAM Improvements

Spin Torque Transfer

• No applied magnetic field• Utilizes heavily spin polarized current• The magnetization of nano-elements is flipped back and forth • Still has challenges in basic physics and materials to overcome

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Applications

Aerospace and military systemsDigital camerasNotebooksSmart cardsCellular base stationsPersonal ComputersBattery-Backed SRAM replacementMedia players

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Referrences

•wikipedia.org/wiki/Magnetoresistive_random-access_memory•www.nve-spintronics.com/mram-Operation•Past, Present and Future of MRAM NIST Magnetic Technology, 22 July 2003•www.sciencemag.org•Masood Qazi “Next Generation MRAM Development“, June 29 2010• Johan Åkerman, "Toward a Universal Memory", Science, Vol. 308. no. 5721 (22 April 2005), pp. 508 – 510, doi:10.1126/science.1110549

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THANK YOU

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