Large anisotropic magnetocaloric effect in all-sputtered epitaxial terbium thin films

• Published in: Physical review materials 2020-12, Vol.4 (12), Article 124404
• Main Authors: El Hadri, Mohammed Salah, Polewczyk, Vincent, Xiao, Yuxuan, Mangin, Stéphane, Fullerton, Eric
• Format: Article
• Language: English
• Subjects: Amorphous materials; Condensed Matter, Materials & Applied Physics; Epitaxial and amorphous material; Epitaxy; Large magnetocaloric effect; Magnetic anisotropy; Magnetic thin films; Magnetocaloric effect; MATERIALS SCIENCE; Rare earth metal; Rare-earth alloys; Sputtering; Terbium; Thin films
• ISSN: 2475-9953; 2475-9953
• DOI: 10.1103/PhysRevMaterials.4.124404

We present an experimental investigation of the magnetic and magnetocaloric properties of sputtered epitaxial and amorphous Tb thin films. We grew epitaxial Nb (50-nm)/Tb (100-nm) bilayer thin films on Al2O3$(11\bar{2}0)$ substrate using DC magnetron sputtering at high temperature, with excellent crystalline quality of the hcp Tb(0001) layer. While the amorphous Tb thin film exhibits more isotropic magnetocaloric properties, we show that the epitaxial Tb thin film displays large anisotropic magnetocaloric properties, with a large maximum magnetic entropy change of 6.27 J kg-1 K-1 at the Néel temperature as well as a large relative cooling power of 225 J kg-1 with a magnetic field change ΔH = 20 kOe applied along the in-plane direction. These large and anisotropic magnetocaloric properties are much larger than those measured for the amorphous Tb thin film, or previously reported for Tb-based thin-film structures. Our findings highlight the opportunities for growing epitaxial rare-earth thin films using sputtering techniques and demonstrate the importance of crystallographic control on the magnetocaloric effect in Tb thin films.