Piezomagnetic and magnetostrictive properties and structure of Fe-CU-Nb-Ta-Si-B alloys annealed in vacuum

Magnetic field dependences of magnetomechanical coupling coefficient and moduli of elasticity in Fe_73.5Cu₁Nb₁Ta₂Si^15.5B₇ alloy in as-quenched state and annealed in vacuum for 1 h at temperatures from 300 to 650 °C were investigated. The maximum changes of the E (ΔE effect), from 102 to 170 GPa, were observed after annealing at 440 °C and from 100 to 165 GPa after annealing at 460 °C. The magnetomechanical coupling coefficient after these heat treatments in the temperature range 440–480 °C was equal to 0.45–0.47. For the-nanocrystalline sample annealed at 560 °C, ΔE was equal to zero, i.e., magnetomechanical coupling vanished. The magnetostriction responsible for these phenomena decreased from about 24 × 10 ⁻⁶ after annealing for 1 h at temperatures of 400–450 °C, to 17 × 10⁻⁶, 6 × 10⁻⁶, about 2 × 10⁻⁶ and nearly zero after annealings at 475, 500, 525 and 550 °C, respectively. The decrease of the magnetostriction is connected with the formation of the nanocrystalline structure.