Magnetoresistive RAM

submited by

Style Pass

2024-12-13 03:00:04

Magnetoresistive random-access memory (MRAM) is a type of non-volatile random-access memory which stores data in magnetic domains.[ 1] Developed in the mid-1980s, proponents have argued that magnetoresistive RAM will eventually surpass competing technologies to become a dominant or even universal memory.[ 2] Currently, memory technologies in use such as flash RAM and DRAM have practical advantages that have so far kept MRAM in a niche role in the market.

Unlike conventional RAM chip technologies, data in MRAM is not stored as electric charge or current flows, but by magnetic storage elements. The elements are formed from two ferromagnetic plates, each of which can hold a magnetization, separated by a thin insulating layer. One of the two plates is a permanent magnet set to a particular polarity; the other plate's magnetization can be changed to match that of an external field to store memory. This configuration is known as a magnetic tunnel junction (MTJ) and is the simplest structure for an MRAM bit. A memory device is built from a grid of such "cells".

The simplest method of reading is accomplished by measuring the electrical resistance of the cell. A particular cell is (typically) selected by powering an associated transistor that switches current from a supply line through the cell to ground. Because of tunnel magnetoresistance, the electrical resistance of the cell changes with the relative orientation of the magnetization in the two plates. By measuring the resulting current, the resistance inside any particular cell can be determined, and from this the magnetization polarity of the writable plate. Typically if the two plates have the same magnetization alignment (low resistance state) this is considered to mean "1", while if the alignment is antiparallel the resistance will be higher (high resistance state) and this means "0".