Spintronics

Spintronics Technology

Submitted To: Presented By :Dr R S Meena Shailendra Kumar Singh Mr Pankaj Shukla C.R. No : 07/126 Final B. Tech. (ECE)

University College Of Engineering, Rajasthan Technical University, Kota.

Presentation On

What Is Spintronics ?• In conventional electronics,

electron charge is used for manipulation, storage, and transfer of information .

• Spintronics uses electron spins in addition to or in place of the electron charge.

Why We Need Spintronics !

Failure of Moore’s Law : Moore’s Law states that the number of transistors on a

silicon chip will roughly double every eighteen months. But now the transistors & other components have reached

nanoscale dimensions and further reducing

the size would lead to:

1. Scorching heat making making the circuit inoperable.

2. Also Quantum effects come into play at nanoscale

dimensions. So the size of transistors & other components cannot be

reduced further.

Basic Principle

In Spintronics , information is carried by orientation of

spin rather than charge. Spin can assume one of the two states relative to the magnetic

field, called spin up or spin down. These states, spin up or spin down, can be used to represent

‘1’ and ‘0’ in binary logic. In certain spintronic materials, spin orientation can be used

as spintronic memory as these orientation do not change

when system is switched off.

Advantage Spintronics

Low power consumption.

Less heat dissipation.

Spintronic memory is non-volatile.

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.

Common metals such as Fe, Al, Ag , etc. can be used.

Gaint Magnetoresistance (GMR) The basic GMR device consists of a layer of non -magnetic metal between two

two magnetic layers. A current consisting of spin-up and spin-down electrons is passed through

the layers. Those oriented in the same direction as the electron spins in a magnetic layer pass

through quite easily while those oriented in the opposite direction are scattered.

SPIN VALVES If the orientation of one of the magnetic layers be changed then

the device will act as a filter, or ‘spin valve’, letting through more

electrons when the spin orientations in the two layers are the same

and fewer when orientations are oppositely aligned. The electrical resistance of the device can therefore be changed

dramatically.

Tunnel Magnetoresistance Magnetic tunnel junction has two

magnetic layers separated by an insulating

metal-oxide layer. Is similar to a GMR spin valve except that

a very thin insulator layer is sandwitched

between magnetic layers instead of metal

layer . The difference in resistance between the

spin-aligned and nonaligned cases is much

greater than for GMR device – infact 1000

times higher than the standard spin valve.

Magnetoresistive Random Access Memory (MRAM)

MRAM uses magnetic storage elements.The elements are mostly tunnel junctions formed from two

ferromagnetic plates, each of which can hold a magnetic field,

separated by a thin insulating layer.

SRAM VS DRAM VS MRAM

SRAM

DRAM

MRAM

Advantage• Fast read & write speed.• Low power

• High density• Fast read &write speed.

• Fast read &write speed.• Low power• High density• Non Volatile

Disadvantage• Volatile• Low density

• Volatile• High power

• None ??

Comparison with DRAM & SRAM In DRAM & SRAM, a bit is represented as charge stored in capacitor. In MRAM, data is stored as magnetic alignment of electrons in a ferromagnetic material. Spin up represents ‘0’ and spin down represents ‘1’. MRAM promises:• Density of DRAM• Speed of SRAM• Non-volatility like flash memory.

That’s why its called universal memory.

256 K MRAM

Journey of MRAM Problems encountered:

1. The density of bits was low.

2. Cost of chips was high. Improved designs to overcome these problems would work

only at liquid nitrogen temperature. An important breakthrough was made in the year 2009. Scientists at the North Carolina State University discovered

a semiconductor material ‘ Galium manganese nitride’ that

can store & retain spin orientation at room temperature. And research is still going on…

Thanks for your attention…!!!

Any Queries ??