What is the difference between Spintronics and GMR Effect?

[Keano16]

Hey all,
First of all, I'm not sure if this is in the right forum-- if not, sorry about that .

I am doing a presentation on Spintronics as part of my 2nd year Physics coursework at University.

In researching, I see that there is a great link between the Giant Magnetoresistance Effect (GMR) and Spintronics. Now to me, the processes seem more or less similar -- changing the spin with magnetic field and writing information.

My question is this: GMR-based devices have been here for a while, such as hard drives, read heads etc... so then WHY is Spintronics said to be such a new field? How exactly are the GMR devices different from the more recent developments in Spintronics??

Thanks.

 

[shawl]

GMR denotes such the special materials which behave a giant difference in resistance under the various magnetic field. One may observe GMR in a composited device and also in some Perovskite materials.

Spintronics is a general concept of the device design, which includes GMR-device, such as spin valves.

In the early study of Spintronics, people use the spin-polarization materials as the electrode of device. But recently they prefer the GMR-materials (Perovskite materials) to make much progress in the development of electronics.

That is an open and virginal field in the device preparation and improvement, as well as the physical mechanism.

 

[sokrates]

Spintronics is a broad field that investigates many other physical phenomena such as Dilute Magnetic Semiconductors, Spin-Orbit Coupling, spin thermoelectricity, spin-torque physics and so on.

The GMR effect is relatively old; but there has been renewed interest in the possibility of developing new technology due to the discovery of spin-transfer-torque recently, around 2005. STT opened a new way to switch magnets, and provided a new mechanism for writing to a magnetic cell. The read-out is done by the usual GMR effect as you may know. But removing highly non-local magnetic fields with a local, precise spin-torque reversal has created a lot of interest.

Hope this helps.

 

[Keano16]

So as I understand it, GMR effect is basically a branch of the broader field that is Spintronics, but the STT allows for further advancement of the field.

Just another thing. In this article http://www.sciencedaily.com/releases/2010/12/101216142511.htm

In the last section, it is mentioned how spin information can now be stored in the nucleus of the atom. But they say that one of the drawbacks is that "spin information is lost" after about 112 seconds.Could you clarify what this might mean.

Thanks very much.

 

[9une]

"Spin information is lost" means that we could read out the information we want after some time. If you once learn something about NMR, you will know this is due to relaxation. We usually consider spin-spin relaxation time(T2) and spin-lattic relaxation time(T1). After a period of time about T1, the spin state will return to the equilibrium state which contains no information. The details about relaxation is still under research.

Hope this helps.

 

[fk08]

The aim of spintronics is to control an injected spin current with an external electric field rather than a magnetic. imagine an spin pointing in positive z-direction that is injected into a Rashba-system, which feautures strong spin-orbit interaction, e.g. the spin orientation depends on the electrons motion. This spin is split into two spins in an perpendicular plane: (1,0) + (0,1). Because these spins have momentum splitting, they will accumulate a phase difference after traveling a distance L. After certain distance the sum of these spins is such that the coherent superposition gives a spin that points along the negative z-direction. Now, if your ferromagnetic drain is magnetized along neg. z-direction you would get a "high conducting" state. Applying an external electric field would change the momentum splitting and thus the spin would not match the orientation of the drain.

electric fields are much easier and "low-energy consumpting" than magentic...

you can also look at the original paper by datta and das in the late 80s