Origin of Ferromagnetism and its pressure and doping dependence in Tl$_{2}$Mn$_{2}$O$_{7}$

TL;DR

This study investigates the origin of ferromagnetism in Tl$_{2}$Mn$_{2}$O$_{7}$, revealing hybridization-driven spin polarization and examining how doping and pressure influence its magnetic transition temperature.

Contribution

It establishes the hybridization mechanism behind ferromagnetism and quantitatively links doping and pressure effects to changes in T$_c$ using first-principles calculations.

Findings

Ferromagnetism is driven by hybridization-induced spin polarization.

Doping with Sb enhances T$_c$, pressure suppresses T$_c$.

Computed T$_c$ values agree with experimental data.

Abstract

Using NMTO-{\it downfolding} technique, we explore and establish the origin of ferromagnetism in the pyrochlore system, Tl$_{2}$Mn$_{2}$O$_{7}$. It is found to be driven by hybridization induced spin-polarization of the delocalized charge carriers derived from Tl-$s$ and O-$p$ states. The mean-field estimate of the ferromagnetic transition temperature, T$_c$, estimated using computed exchange integrals are found to be in good agreement with the measurements. We find an enhancement of T$_{c}$ for moderate doping with nonmagnetic Sb and a suppression of T$_{c}$ upon application of pressure, both in agreement with experimental findings.