A semi empirical approach to the analysis of the susceptibility data of frustrated magnets

• Grant number: 19/27555-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2020
• End date: December 31, 2021
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Fernando Assis Garcia
• Grantee: Lauro Barreto Braz
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The determination of the energy scale of the magnetic interactions is an important step in the study of frustrated magnets. The usual approach to this problem is to fit the system's magnetic susceptibility to the Curie-Weiss law. The fitting renders the Curie-Weiss constant which, in turn, can be connected to the exchange interaction between localized spins in the solid. For solids hosting magnetic isolated magnetic clusters, however, the connection of the Curie-Weiss constant and the actual exchange constants is meaningless. To contribute to this problem, our project proposes the development of a semi-empirical approach, based upon the determination of a microscopic Hamiltonian that describes the magnetic interaction within the clusters. Using this microscopic Hamiltonian, one can calculate the susceptibility as function of suitable exchange parameters $J_n$ and apply it to fit experiments. In this project, we shall consider clusters of magnetic dimers, trimers and quadramers as can be observed in BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$, Ba$_{4}$ScMn$_{3}$O$_{12-y}$ and Ba$_{5}$YMn$_{4}$O$_{15-y}$, all of which are candidates to host exotic magnetic ground states. The present project, while primarily intended for an introduction to the field of condensed matter physics, addresses a hot topic in the field, with the perspective of contributing to the state of the art of magnetically frustrated systems.