Magnetic phase diagram of Ce2Fe17

TL;DR

This study investigates the complex magnetic phase behavior of Ce2Fe17 and Ta-doped Ce2Fe17, revealing multiple magnetic phases and constructing detailed phase diagrams to understand the interplay of ferromagnetic and antiferromagnetic interactions.

Contribution

The paper provides the first detailed magnetic phase diagrams of Ce2Fe17 and Ta-doped Ce2Fe17, explaining their anomalous magnetic properties through a theory of competing magnetic interactions.

Findings

Ce2Fe17 exhibits two magnetic transition temperatures, TN and TT.

Ta doping introduces an additional ferromagnetic phase at T0.

Magnetic phase diagrams align well with a theory of competing antiferro- and ferromagnetism.

Abstract

Rare-earth-based permanent-magnet materials rich in iron have relatively low ferromagnetic ordering temperatures. This is believed to be due to the presence of antiferromagnetic exchange interactions, besides the ferromagnetic interactions responsible for the magnetic order. The magnetic properties of Ce2Fe17 are anomalous. Instead of ferromagnetic, it is antiferromagnetic, and instead of one ordering temperature, it shows two, at the Neel temperature TN ~ 208 K and at TT ~ 124 K. Ce2Fe17, doped by 0.5% Ta, also shows two ordering temperatures, one to an antiferromagnetic phase, at TN ~ 214 K, and one to a ferromagnetic phase, at T0 ~ 75 K. In order to clarify this behavior, single-crystalline samples were prepared by solution growth, and characterized by electron microscopy, single crystal x-ray diffraction, temperature-dependent specific heat, and magnetic field and temperature-dependent electrical resistivity and magnetization. From these measurements, magnetic H-T phase diagrams were determined for both Ta-doped Ce2Fe17 and undoped Ce2Fe17. These phase diagrams can be very well described in terms of a theory that gives magnetic phase diagrams of systems with competing antiferro- and ferromagnetism.