Wave reversal mode: A new magnetization reversal mechanism in magnetic nanotubes

RAVIOLO, SOFÍA; DIANA ARCINIEGAS JAIMES; BAJALES NOELIA; ESCRIG, JUAN

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2020 vol. 497

0304-8853

We have investigated the magnetic properties of 14nm thick and 1μm long nickel and permalloy nanotubes with external diameters of 40 and 100nm as a function of the angle θ at which the external magnetic field is applied. Our results show that the coercivity of 40nm diameter nickel nanotubes follows a non-monotonic behavior from θ=0° up to θ=60°, while that corresponding to permalloy displays an increasing monotonic trend at the same angular range. At θ=90°, both materials evidence a sharp drop of the coercivity to zero, indicating that the reversal mechanism has changed to a pseudo-coherent rotation. On the other hand, nickel and permalloy nanotubes with 100nm in diameter exhibit a similar angular dependence of the coercivity, reversing their magnetization through the nucleation and propagation of vortex domain walls for angles lower than 75°. For θ=90°, a novel striking mechanism, the wave reversal mode (W), arises. This phenomenon leads to an unusual S-type shape in the hysteresis curves at those given parameters, which is until now an effect that has not been reported for these nanostructures.