Table-like magnetocaloric effect and enhanced refrigerant capacity in EuO1-{\delta} thin films

TL;DR

This study demonstrates that EuO1-{ extdelta} thin films with controlled oxygen vacancies exhibit enhanced and table-like magnetocaloric effects, making them promising for efficient small-scale magnetic refrigeration near liquid nitrogen temperatures.

Contribution

It introduces a method to tune the magnetocaloric response of EuO1-{ extdelta} thin films via oxygen vacancy control, achieving superior refrigerant capacity compared to bulk EuO.

Findings

Maximum magnetic entropy change of 6.4 J/kg K at 2 T

Refrigerant capacity exceeds that of bulk EuO

Oxygen vacancies induce table-like magnetocaloric effects

Abstract

An approach to adjusting the conduction band population for tuning the magnetic and magnetocaloric response of EuO1-{\delta} thin films through control of oxygen vacancies ({\delta} = 0, 0.025, and 0.09) is presented. The films each showed a paramagnetic to ferromagnetic transition around 65 K, with an additional magnetic ordering transition at higher temperatures in the oxygen deficient samples. All transitions are observed to be of second order. A maximum magnetic entropy change of 6.4 J/kg K over a field change of 2 T with a refrigerant capacity of 223 J/kg was found in the sample with {\delta} = 0, and in all cases the refrigerant capacities of the thin films under study were found to exceed that reported for bulk EuO. Adjusting the oxygen content was shown to produce table-like magnetocaloric effects, desirable for ideal Ericsson-cycle magnetic refrigeration. These films are thus excellent candidates for small-scale magnetic cooling technology in the liquid nitrogen temperature range.