Chapter 9 - Rare-Earth Magnetocaloric Thin Films

Abstract

Magnetocaloric materials exhibit first-order phase transition and also exhibit extreme property changes at the first-order magnetostructural phase transition including a giant magnetocaloric effect close to room temperature. These interesting properties have been broadly studied (Pecharsky and Gschneidner [1]; Pecharsky and Gschneidner [2]; Mudryk et al. [3]; Hadimani et al. [4–6]; Hadimania and Jiles [7,8]; Hadimani et al. [9–11]), yet all of the past research has been concerned with bulk materials. Thin films of these strain sensitive materials, if they can be prepared and protected from oxidation in ambient conditions, will open up new science ranging from strain-controlled magnetism to functionally graded materials. High-quality thin films that are protected from oxidation and are stable at ambient conditions will exhibit material properties in the vicinity of the unusual phase transitions. There have been several attempts to prepare stable rare-earth magnetocaloric thin films that exhibit giant magnetocaloric effect. Some have failed or others have not been able to show giant magnetocaloric effect exhibited by their bulk materials (Sambandam et al. [12]). Recent publication by Hadimani et al. showed that Gd5Si1.3Ge2.7 thin film retains the magnetostructural transition as observed in its bulk counterpart. It shows a broader magnetic response than the bulk target, exhibiting a lower entropy change but a higher FWHM and a large magnetic hysteretic losses reduction (Hadimani et al. [13]).