In the case of the non-local spin detection, the spin current is detected aside of the flow of the drift charge current.

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Non-Local spin detection

In this case the spin accumulation is injected from a ferromagnetic metal (injector) into a non-magnetic metal. A voltage is applied between the injector and a remote contact on the non-magnetic metal.

For the spin detection an electrode fabricated close to the injector is used. The detection voltage is measured between the detector and a remote contact on the non-magnetic metal, which is far from the flow of the drift current.

Note: The detection electrode can be made either from a ferromagnetic metal or from a non-magnetic metal. Often it is made from a ferromagnetic metal and the detection voltage is measured as a function of mutual magnetization directions of the detector and the injector.

 

 

Calculate by yourself. It is easy!!!

Download Comsol file here

 

 

 

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Fabrication

For this experiment the small sizes of nano contacts and a narrow gap between the injector and the detector are important.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Calculations

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The injection into volume of the non-magnetic metal.

It is case when the injection conductivity of the same sign in the ferromagnetic metal and the non-magnetic metal. For example, in both metals the conductivity of the electron type or in both metals the conductivity of the hole type.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

As the injection current increases, the spin accumulation in the vicinity of the detector increases. It causes the increase of the detection voltage.

For the opposite direction of the drift current in the injector, the spin accumulation is depleted in the vicinity of the detector and the detection voltage decreases.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Diffusion Spin current. In the case of the injection, it increases in the vicinity of the injector. Since the detector is made close to the injector, there is an increase of the spin current in the vicinity of the detector as well.

For the opposite direction of the drift current, the spin accumulation is depleted in the vicinity of the injector and some spin accumulation is pumped out from the region in the vicinity of the detector.

(Note, the spin current on top of injector and at left side of the non-magnetic metal is due to imperfect transparent boundary conditions)

 

Diffusion Charge Current. It occurs because of the non-zero detection conductivity. It changes significantly in the vicinity of the injector, but it changes only slightly in the vicinity of the detector.

Drift Charge Current. There is no drift charge current in the vicinity of the detector.

 

 

 

 

 

Accumulated Charge. The spin detection occurs because the charge accumulation along spin diffusion.

There are spin-dependent and spin-independent charge accumulation. The spin-independent charge accumulation occurs in regions where there is a gradient of conductivity and a drift current flows. The spin-independent charge accumulation disturbs the spin detection.

In the vicinity of the injector the charge accumulation is mainly spin-independent. In the vicinity of the detector the charge accumulation is spin-dependent.

 

 

 

 

 

 

 

Charge Conductivity. In this example, it is the same for the injector, the detector and the non-magnetic metal. In the vicinity of the contacts the conductivity monotonically decreases, has a minimum at the contact and next increases. There is no step-like changes of the conductivities.

Injection Conductivity. It has the same sign for or the injector, the detector and the non-magnetic metal. It is proportional to the charge conductivity.

Detection Conductivity. It equals to zero in the bulk of the metals and it is non-zero in the vicinity of the contacts.

 

 

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Spin Diffusion Length

It changes with the change of the injector current in the region when drift current flows (injector region). It does not change in the region where there is no drift current (detection region)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The yellow squares show position of the injector (left square) and the detector (right square)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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