Magnetic and magnetocaloric properties of Fe2Ta thin films

S Shaji,D Kumar,P Giri,C Binek,Nikhil R Mucha

doi:10.1063/1.5134796

Abstract

A magnetocaloric effect (MCE) on rare-earth free Fe2Ta thin films is reported. The structural characterizations carried out using x-ray diffraction and transmission electron microscopy have indicated the formation of a Laves phase in the Fe2Ta film in a MgZn2 type crystal structure. Applying the Maxwell relation to the magnetization (M) vs temperature (T) curves at various fields (H), ∂M/∂T vs H curves were integrated to indirectly obtain quantitative information about the isothermal entropy change. A positive MCE with an entropy change as high as 6.9 J/K m3 at 10 K and a negative MCE with an entropy change as high as −2.0 J/K m3 at 300 K were observed for the magnetic fields in the range of 0.05–0.5 T. The temperatures at which a crossover in the sign of the entropy change takes place were found to be a function of the field applied that ranged from 121 K at 5000 Oe to 159 K at 1000 Oe. The coexistence of the positive and negative MCE is attributed to a paramagnetic–antiferromagnetic transition in the Fe2Ta system.

Highlights

There is a strong need to develop new material systems and technologies with efficient refrigeration capability to reduce energy consumption without leaving any footprint on the environment
We report the observation of an magnetocaloric effect (MCE) in pulsed laser deposited rare-earth free magnetic Fe67Ta33 alloy thin films, where subscript numbers 67 and 33 indicate the chemical composition of the alloy in atomic percentage, which is an average value of 25 sites on the Fe–Ta thin film obtained using x-ray fluorescence (XRF) analysis
The selection of the Fe2Ta composition is based on its existence as a single phase in the Fe–Ta phase diagram

Summary

Introduction

There is a strong need to develop new material systems and technologies with efficient refrigeration capability to reduce energy consumption without leaving any footprint on the environment.1–5. In terms of atomic percentage, this composition is expressed as Fe96.7Ta3.3 with a chemical formula of Fe29Ta. The level of Ta doping is much higher in the present work, but the phase is scitation.org/journal/adv still a single phase.

Results

Conclusion