WEBVTT

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Today we're learning about "MRAM" with Daniela at NVE. So, Danno, what is "MRAM"?

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MRAM stands for Magnetoresistive Random Access Memory.

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Unlike semiconductor memories that use electron charge to store data,

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 MRAM uses electron spin.

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Why is that better?

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Unlike charge, electron spin is inherently
permanent. MRAM has been called

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the ideal memory because of its potential to combine the speed of SRAM, the density of DRAM, and

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the nonvolatility of flash memory.

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So how does it work?

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Let's look at what's called "classical" MRAM.

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Each bit has a spin-dependent tunnel junction
memory cell, 

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and magnetic row and column write lines. 

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The spin-dependent tunnel junction

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produces a large change in resistance, depending on the predominant electron spin in a storage layer.

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The tunnel barrier is as thin as a
few atomic layers. 

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It's so thin, that depending on spin polarizations, 

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electrons can "tunnel"
through the normally insulating material,

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causing a resistance change.

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Here's an SEM of an actual tunnel junction
made here at NVE. 

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This white stripe is an aluminum-oxide tunnel barrier, eight atoms thick. 

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This is probably magnified nearly a million times
on your screen, 

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so an eight-inch wafer
would appear a hundred miles in diameter.

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We have a separate video explaining "tunnel junctions."

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So, in MRAM, data is read as
the tunnel junction resistance. 

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Data is stored in the spin-polarization

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of a tunnel junction magnetic layer. 

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The write lines create magnetic fields that

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store data bits by setting magnetic spin polarization.

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So what's after "classical MRAM"?

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Next-generation MRAM could reduce cell size and power consumption. 

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One next-generation technology is
Spin-Momentum Transfer, 

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which changes the spin of storage electrons directly

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with a spin-polarized electrical current,
rather than an induced magnetic field.

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This has the potential to significantly reduce
MRAM write currents and self-heating.

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Thanks, Danno—that was "memorable."

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Go to nve.com for more info on MRAM and spintronics.