Investigating Distorted Hysteresis Loop Of NiFe Film Based On Vibrating Sampie Magnetometer With Two Pickup Coils

Distorted hysteresis loop,such as inverted loop,may be observed in measurements performed by using Vibrating Sample Magnetometer(VSM).This is related to the operating principle and configuration of VSM as well as the anisotropy and orientation of sample.In this dissertation,we investigate the effect of depositing progress on the structural and magnetic properties of NiFe alloy film,and achieve a well-defined uniaxial anisotropy in NiFe films.Then,the out-of-plane hysteresis loops of these films are measured by using VSM with two pickup coils.In the out-of-plane measurements,we may find another kind of distorted loop,which has normal round but exhibits two approximately symmetrical peaks near zero field,that is,there exists a small range of measuring field in which negative susceptibility occurs.This distortion is unlikely ascribed to the sample displacement because the sample is located within the saddle range before measurement.Considering that the VSM actually gives the magnetic moment component along the vibrating direction and its dependence on the measuring field is recorded as the nominal hysteresis loop,we propose a mechanism explaining this kind of distortion: the directions of vibrating,measuring field,normal of sample film slightly deviate away from each other,in which case the moment component along vibrating direction should show some increase when the in-plane anisotropic axis lies in a certain range of azimuthal angle.