Magnetostrictive Behaviors of fcc-Co(001) Single-Crystal Films Under Rotating Magnetic Fields

Abstract

  Magnetostrictive behaviors of fcc-Co(001) single-crystal films with thicknesses ranging from 40 to 500 nm are investigated under rotating magnetic fields up to 1.2 kOe. The magnetocrystalline anisotropy estimated from the magnetization curves is confirmed to be lying with four-fold symmetry, and the anisotropy field is within a narrow range of 900~950 Oe for these films. The easy and the hard axes are lying parallel to <110> and <100>, respectively. The magnetostrictive behavior measured along [110] shows rectangular or bathtub-like waveform and the amplitude does not change much when the magnetic field is increased. On the contrary, the behavior along [100] shows triangular waveform and the amplitude increases with increasing the magnetic field. These characteristic behaviors are explained by using a coherent rotation model of magnetization assuming an in-plane four-fold magnetic anisotropy. The magnetostriction constants (λ₁₀₀, λ₁₁₁) estimated from the amplitudes measured at 1.2 kOe are λ₁₀₀=(85~90)×10⁻⁶ and λ₁₁₁=−(40~50)×10⁻⁶, respectively for these films. The λ₁₀₀ values are in agreement with that estimated by the first-principle calculation.