15-03-2011, 02:31 PM
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Magnetoresistive Random Access Memory (MRAM)
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.
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.
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.
Fe/MgO/Fe junctions reach over 200% decrease in electrical resistance at room temperature
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.
• 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 of the same spin of the second film.
Spin Valve GMR
• Hard layer: magnetization is fixed.
• Soft layer: magnetization is free to rotate.
• Thin non-ferromagnetic spacer ~3 nm.
• Spacer material Cu (copper) and ferromagnetic layers NiFe (permalloy).
• This configuration used in hard drives
Magnetic Tunnel Junction (MTJ)
MRAM
MRAM: Fixed layer
MRAM: Reading process
MRAM: Writing process
MRAM: Characteristics
Other RAM Technologies
MRAM Vs Other RAM Technologies
Future MRAM Improvements
MRAM Status
Magnetoresistive Random Access Memory (MRAM)
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.
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.
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.
Fe/MgO/Fe junctions reach over 200% decrease in electrical resistance at room temperature
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.
• 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 of the same spin of the second film.
Spin Valve GMR
• Hard layer: magnetization is fixed.
• Soft layer: magnetization is free to rotate.
• Thin non-ferromagnetic spacer ~3 nm.
• Spacer material Cu (copper) and ferromagnetic layers NiFe (permalloy).
• This configuration used in hard drives
Magnetic Tunnel Junction (MTJ)
MRAM
MRAM: Fixed layer
MRAM: Reading process
MRAM: Writing process
MRAM: Characteristics
Other RAM Technologies
MRAM Vs Other RAM Technologies
Future MRAM Improvements
MRAM Status
