Proximity Effects in Py-Cu Composite Spin Valves with Temperature Dependent Coupling

We present results on an exchange biased spin valve whose interlayer undergoes a magnetic phase transition. The structure consisted of 3 variations of Py_xCu_1-x: Py_0.8Cu_0.2/Py_0.4Cu_0.6/Py_1.0Cu₀/IrMn. The IrMn serves to exchange bias the Py layer; the degree to which the rest of the sample exhibits exchange bias depends on ferromagnetic coupling between the Py_xCu_1-x layers. Magnetization and angle with respect to temperature (M v. T and φ_M v. T, respectively) measurements from polarized neutron reflectometry (PNR) indicate a sharp transition temperature at T = 160 K, which is the Curie temperature (TC) of the spacer layer. Below this, both the Py_0.8Cu_0.2 and Py layers exhibit exchange bias. As the temperature increases and the system approaches 160 K, the portion of the loop corresponding to the bottom free layer (Py_0.8Cu_0.2) shifts closer to zero, showing a Néel-like transition. When T > 160 K, the coupling between the top and bottom layers is broken, and EB is only observed for the Py layer in direct contact with IrMn. Additional measurements studying the dependence on layer thickness will be reported.