Magnetoimpedance hysteresis in amorphous microwires induced by core-shell interaction

We report on magneto-impedance (MI) hysteresis at MHz and GHz frequencies in amorphous microwires subject to a sufficiently high applied axial magnetic field H-E. We show that this hysteresis originates from the magnetic hysteresis of the inner core which biases the outer shell causing a shift of the MI curve along the H-E axis. Combined experiments (longitudinal and off-diagonal MI Z(H-E), hysteresis loops M(H-E) by vibrating sample magnetometer, and induction method) reveal the details of the magnetization reversal process in these microwires: Partial field dependencies Z(H-E) and M(H-E) are shown to be practically anhysteretic but shifted to the left or to the right about the origin by a residual magnetic field of the inner core H-C. This shift can vary in the range from -35 to +35 A/m, depending on the magnetic history of the sample. We demonstrate that the hysteresis can be suppressed by application of a high enough axial magnetic field that saturates the magnetization of the inner core. A potential application of this hysteresis for memory devices is also proposed. (C) 2014 AIP Publishing LLC.