Nonlocal Spin Valves in Metallic Nanostructures

In Section 32.2, we describe the basic aspect of spin injection, spin accumulation, and spin current in lateral devices comprising of nonmagnetic and ferromagnetic metals. We introduce the concept of the spin resistance, that is, a measure of impedance against spin relaxation; thereby lateral spin valve structures can be expressed by equivalent spin-resistance circuits in analogy with cascaded transmission lines. This certainly facilitates designing the lateral spin valves exhibiting efficient spin injection and detection. In Section 32.3, we put our focus on the effect of the device structure, including the junction size, on the magnitude of the spin accumulation stored in the nonmagnet and also the magnitude of the spin current flowing in it. This implies that the spin injection efficiency can be tuned by connecting materials with appropriate structures and spin resistances.