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PowerPoint Presentation On Magnetic Core RAM



  • Introduction
  • Magnetic RAM -A historical overview
  • Why MRAM ???
  • Magnetic core RAM
  • Basic principle
  • Magnetoresistance
    • Giant Magnetoresistance (GMR)
    • Tunnel Magnetoresistance (TMR)
  • MRAM
    • Fixed Layer
    • Reading Process
    • Writing Process
    • Characteristics
    • interference
  • Other RAM Technologies-DRAM,SRAM,FLASH RAM
  • MRAM Vs Other RAM Technologies
  • Applications
  • Future MRAM Improvements

  • By the early 1960s, Magnetic Core RAM became largely universal as main memory, replacing drum memory
  • MRAM uses magnetism rather than electrical power to store bits of data.
  • Ferro-magnet
Ferro-magnet is the type
  • of material used to develop
  • MRAM
  • MRAM A Historical Overview
  • 2003 - A 128 kbit MRAM chip was introduced, manufactured with a 180 nm lithographic process
  • 2004 - Infineon unveiled a 16-Mbit prototype, manufactured with a 180 nm lithographic process
  • 2005 - Sony announced the first lab-produced spin-torque-transfer MRAM
  • 2007 - Tohoku University and Hitachi developed a prototype 2 Mbit Non-Volatile RAM Chip employing spin-transfer torque switching
  • 2008 - Scientists in Germany have developed next-generation MRAM that is said to operate 

Why MRAM ???
  • Why MRAM Became an Important Research Topic
    • Universal Memory (Computing & Electronics)
    • Instant-On Computing
    • Read & Write to Memory Faster
    • Reduced Power Consumption
    • Save Data in Case of a Power Failure
  • Modern MRAM Technology Emerged from Several Technologies :
    • Magnetic Core Memory
    • Magnetoresistive RAM
    • Giant Magnetoresistance
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 

Basic Principle
The 2 Possible Magnetization States of a Ferromagnetic Element can be Described by a Hysteresis Loop

Magnetization of Film vs.
* The 2 Possible Magnetization States of a Ferromagnetic Element can be Described by a Hysteresis Loop

* Two important concepts of MRAM


Giant Magnetoresistance (GMR)

Two thin films of altering ferromagnetic materials and a non-magnetic layer-spacer.

Tunnel Magnetoresistance (TMR)

* Two thin films of altering ferromagnetic materials and an insulating spacer.

* In ferromagnetic metals electronic bands are exchange split which implies different densities of states at the Fermi energy for the up- and down-spin electrons.

Tunnel Magnetoresistance (TMR)

* Spin of electrons is conserved in the tunneling process.
* Tunneling of up- and down-spin electrons are two independent processes → conductance occurs in the two independent spin channels.
* Electrons originating from one spin state of the first ferromagnetic film are accepted by unfilled states

Magnetic Tunnel Junction (MTJ)
Commonly used insulating materials are Aluminum oxide (Al2O3) and crystalline Magnesium oxide (MgO)

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.

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.

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.

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.

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.

MRAM: Characteristics

* Non-volatility

* Infinite endurance

* High speed performance

* Low cost


* Interference between adjacent cells
* Disturbance by digit line current to adjacent line current
* The effect of heat cause bit flip
* Risks of leaking current and other

Other RAM Technologies
Each bit of data is stored in a separate capacitor within an integrated circuit


* Volatile
* The highest density RAM currently available
* The least expensive one
* Moderately fast

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


* Expensive
* Volatile
* Fast
* Low power consumption
* Less dense than DRAM

Other RAM Technologies

Flash RAM

Stores information in an array of memory cells made from floating-gate transistors


* Cheap
* Non-volatile
* Slow
* Enormously durable
* Limited endurance

* Digital camera
* Cellular phones
* Palm pilot
* MP3

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

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

# Bonsor, Kevin. How Magnetic RAM Will Work. 9 Feb 2003. .
# Daughton, James. Magnetoresistive Random Access Memory (MRAM). 4 Feb 2000. 1-13. 13 Feb 2003. .
# Goodwins, Rupert. Magnetic Memory Set to Charge the Market. ZDNet UK. 12 Feb 2003. 16 Feb 2003. .
# Guth, M., Schmerber, G., Dinia, A. “Magnetic Tunnel Junctions for Magnetic Random Access Memory Applications.” Materials Science and Engineering. Online 2 Jan 2002: 19. Science Direct. 16 Feb 2003. .
# IBM Magnetic RAM Images. 16 Feb 2003. .
# Johnson, Mark. “Magnetoelectronic memories last and last.” IEEE Spectrum 37 (2000 Feb): 33-40.

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