Delayed demagnetization jumps in (NdDy)(FeCo)B magnets in a steady-state magnetic field

Abstract

Spontaneous demagnetization jumps are observed in sintered magnets (Nd_0.6Dy_0.4)₁₆(Fe_0.77Co_0.23)₇₈B₆ in a constant magnetic field after a sharp decrease in an external magnetic field from the value corresponding to the saturation to a value close to the coercive force. It is shown that the number of the magnetization jumps is proportional to their amplitudes. A low value of the autocorrelation coefficient between the jump amplitude and the time of its appearance (R < 0.1) demonstrate the stochasticity of the jumps. It is found that the spectral jump density is independent of the frequency, i.e., a white magnetic noise is observed. The distribution of the magnetic field gradient has been obtained near the sample surface that makes it possible to distinguish domains and the grain magnetization in the dependence on the direction of the texturing of the sintered magnet.