Exploring Linear and Non-linear AC susceptibilities of Single Crystal Gadolinium around Curie & Spin-reorientation transitions

Abstract

The aim of this project is to probe the characteristic magnetic properties of elemental gadolinium using the technique of AC magnetic susceptibility. To this end, a home made AC susceptometer was used to probe a polycrystalline and a single crystal gadolinium sample, in the temperature range of 100K to 300K. The first and third order susceptibility of these samples were measured so as to understand the behaviour of gadolinium in the vicinity of two critical transitions: the spin reorientation transition and the Curie transition. To the best of our knowledge, 3rd harmonic susceptibility around these transitions is yet not reported, especially in single crystal samples. While both the samples show a subtle feature around TSR in the first harmonic susceptibility, a sharp feature in the form of cross over around TC is detected in the third harmonic. Interestingly, previous studies have shown that the sign of the cross-over is reversed in polycrystalline Gd, which we also observe. However the 3rd harmonic susceptibility in the single crystal reveals a new feature, just above the TC , in addition to the cross-over phenomenon. The 3rd harmonic susceptibility exhibits much sharper transition in the vicinity of the spin-reorientation transition in both polycrystalline and single crystal Gd as compared to what is observed in first harmonic susceptibility . Our data brings forward the importance of higher harmonic susceptibility in exploring complex ferromanet such as Gd, in which interest is rekindled due to a recent report about the possibility of topological magnons