Tuning Metallic Ferromagnets via Pressure and Substitution

Abstract

Early observation of magnetism began over 2000 years ago with ``natural'' magnets magnetite and iron.These materials, when found in a magnetized state, would attract other objects of the same or similar materials, as well as attention in and outside of academia.This attraction became a definitive feature of ferromagnetism.To physicists in particular, ferromagnetism fascinates for furnishing an example of quantum-level mechanisms not only resulting in macro-scale effects, but doing so in a way obvious even to an untrained eye.Despite the long history of study of ferromagnetism, many fundamental questions remain, and research continues into the modern day.More recent investigations examine subjects such as how to predict transition temperatures, effects of order and disorder on magnetic properties, and the properties that arise when a magnetic transition approaches 0 K, among many others.This work examines a number of these questions of ferromagnetic order through experiments on three example compounds: NiPd, CePd₂P₂, and CrMnFeCoNi.The studies on NiPd present an example of the effects of chemical substitution -- a "disordered" tuning parameter -- on a ferromagnetic transition.The properties of CePd₂P₂ were examined using the "clean" parameter of applied pressure, and the results of these two studies can be compared and contrasted.Finally, CrMnFeCoNi, known as the equiatomic Cantor alloy, is an extremely disordered system with competing magnetic interactions between its constituent atoms, and provides an example of magnetic ordering in the relatively novel class of compounds known as "high-entropy" alloys.