Compensated Ferrimagnets for Spintronic Applications

Abstract

Antiferromagnetic spintronics is increasingly in vogue owing to advantages like the relative insensitivity of these systems to external magnetic fields, and the ultrafast nature of their spin dynamics which can have a number of potential uses. In this context, compensated ferrimagnets are also attracting increasing attention, due to the fact that they combine some of the advantages of both the ferro and antiferro- magnetically ordered systems. Intrinsically antiferromagnetic with two uncompensated sub-lattices, the bulk magnetization of such systems can be tuned to zero using number of external parameters like chemical substitution, strain, temperature etc. In this project, we investigated some garnet compositions (ferrites of the form A3Fe3O12 , where A is a rare earth), namely Gadolinium Iron Garnet(Gd3Fe5O12), Yttrium Iron Garnet(Y3Fe5O12) and Ytterbium Iron Garnet(Yb3Fe5O12) with the aim of evaluating their potential as spintronic materials. The di erent garnet compositions were synthesised via the solid state route, with the aim of tuning the compensation temperature to be very close to room temperatures, this was achieved by doping Gd3Fe5O12 with ”Mn” of di erent concentrations on the octahedral ”Fe” site. The temperature and field dependent spin transport in these bulk systems were investigated using Spin Seebeck measurements. 5