Spin does not replace charge current just provide extra controlUsing suitable materials, many different “bit” states can be interpreted
University College Of Engineering, Rajasthan Technical University, Kota.<br />Presentation <br /> On<br />Spintronics Technology <br />Submitted To: Presented By :<br />Dr R S MeenaShailendra Kumar Singh MrPankajShukla C.R. No : 07/126 Final B. Tech. (ECE)<br />
What Is Spintronics ?<br />In conventional electronics, electron charge is used for manipulation, storage, and transfer of information .<br />Spintronics uses electron spins in addition to or in place of the electron charge.<br />
Why We Need Spintronics !<br />Failure of Moore’s Law :<br /><ul><li> Moore’s Law states that the number of transistors on a</li></ul> silicon chip will roughly double every eighteen months.<br /><ul><li> But now the transistors & other components have reached </li></ul>nanoscale dimensions and further reducing<br /> the size would lead to:<br /> 1. Scorching heat making making the circuit inoperable.<br /> 2. Also Quantum effects come into play at nanoscale<br /> dimensions.<br /><ul><li>So the size of transistors & other components cannot be </li></ul> reduced further.<br />
Basic Principle<br /><ul><li> In Spintronics , information is carried by orientation of </li></ul> spin rather than charge.<br /><ul><li> Spin can assume one of the two states relative to the magnetic </li></ul> field, called spin up or spin down.<br /><ul><li> These states, spin up or spin down, can be used to represent </li></ul> ‘1’ and ‘0’ in binary logic. <br /><ul><li> In certain spintronic materials, spin orientation can be used </li></ul> as spintronic memory as these orientation do not change <br />when system is switched off.<br />
Advantage Spintronics<br /><ul><li> Low power consumption.
Takes up lesser space on chip, thus more compact.
Spin manipulation is faster , so greater read & write speed.
Spintronics does not require unique and specialized semiconductors. </li></ul> Common metals such as Fe, Al, Ag , etc. can beused.<br />
GaintMagnetoresistance (GMR)<br /><ul><li>The basic GMR device consists of a layer of non -magnetic metal between two</li></ul> two magnetic layers.<br /><ul><li> A current consisting of spin-up and spin-down electrons is passed through</li></ul> the layers.<br /><ul><li> Those oriented in the same direction as the electron spins in a magnetic layer pass </li></ul> through quite easily while those oriented in the opposite direction are scattered.<br />
SPIN VALVES<br /><ul><li>If the orientation of one of the magnetic layers be changed then </li></ul> the device will act as a filter, or ‘spin valve’, letting through more <br /> electrons when the spin orientations in the two layers are the same <br /> and fewer when orientations are oppositely aligned. <br /><ul><li>The electrical resistance of the device can therefore be changed </li></ul> dramatically.<br />
Tunnel Magnetoresistance<br /><ul><li> Magnetic tunnel junction has two </li></ul> magnetic layers separated by an insulating <br />metal-oxide layer.<br /><ul><li> Is similar to a GMR spin valve except that </li></ul> a very thin insulator layer is sandwitched<br /> between magnetic layers instead of metal <br /> layer .<br /><ul><li> The difference in resistance between the </li></ul> spin-aligned and nonaligned cases is much <br /> greater than for GMR device – infact 1000 <br /> times higher than the standard spin valve.<br />
Magnetoresistive Random Access Memory (MRAM)<br /><ul><li> MRAM uses magnetic storage elements.
The elements are mostly tunnel junctions formed from two </li></ul> ferromagnetic plates, each of which can hold a magnetic field, <br /> separated by a thin insulating layer.<br />
SRAM VS DRAM VS MRAM<br />SRAM<br />DRAM<br />MRAM<br />Advantage<br /><ul><li> Fast read & write </li></ul> speed.<br /><ul><li> Low power
None ??</li></li></ul><li>Comparison with DRAM & SRAM<br /><ul><li> In DRAM & SRAM, a bit is represented as charge stored in </li></ul> capacitor.<br /><ul><li> In MRAM, data is stored as magnetic alignment of electrons in</li></ul> a ferromagnetic material. Spin up represents ‘0’ and spin down<br /> represents ‘1’.<br /><ul><li> MRAM promises:
That’s why its called universal memory.</li></ul>256 K MRAM<br />
Journey of MRAM<br /><ul><li>Problems encountered:</li></ul> 1. The density of bits was low.<br /> 2. Cost of chips was high.<br /><ul><li> Improved designs to overcome these problems would work </li></ul> only at liquid nitrogen temperature.<br /><ul><li> An important breakthrough was made in the year 2009.
Scientists at the North Carolina State University discovered</li></ul> a semiconductor material ‘ Galium manganese nitride’ that <br /> can store & retain spin orientation at room temperature. <br /><ul><li> And research is still going on… </li></li></ul><li>Thanks for your attention…!!!<br />Any Queries ??<br />