Higher-order magnetic anisotropy in soft-hard magnetic materials

Abstract

We have computationally studied the properties of higher-order magnetic anisotropy constants in an L1 0 /A1-FePt core-shell system which is characterized by a strong second-order two-ion Fe-Pt anisotropy component. We show that the core-shell structure induces an unexpected fourth-order anisotropy constant K 2 , the magnitude of which varies nonmonotonically with the core-size ratio R reaching a peak at R ≈ 0.50. Furthermore, we find that K 2 scales with the normalized magnetization by (M/M s ) 2.2 at temperatures below the Curie temperature, a remarkable deviation from the established Callen-Callen theory which instead predicts a scaling exponent of 10. We construct an analytic model which demonstrates K 2 arises from the canting of the core and shell magnetization, and successfully reproduces and justifies the scaling exponent obtained from numerical simulation.

High Temperature and FORC Investigations of Semiconducting/Ferromagnetic Nanocomposites

“…Magnetic coupling between the particles at room temperature can be excluded due to the corresponding FORC diagram (see figure 4). Generally, TC decreases with decreasing particle size which can be explained by finite size effects (18). A NiCo alloy is deposited within porous silicon mainly in the near surface region (figure 5).…”