Magnetic field dependence of the maximum magnetic entropy change

TitleMagnetic field dependence of the maximum magnetic entropy change
Publication TypeJournal Article
Year of Publication2011
AuthorsLyubina J, Kuz'min MD, Nenkov K, Gutfleisch O, Richter M, Schlagel DL, Lograsso TA, Gschneidner KA
Journal TitlePhysical Review B
Date Published01
Type of ArticleArticle
ISBN Number1098-0121
Accession NumberISI:000286740800001
Keywords2nd-order phase-transition

The maximum isothermal entropy change in a magnetic refrigerant with a second-order phase transition is shown to depend on applied magnetic field H as follows: (-Delta S)(max) = A(H + H-0)(2/3)-AH(0)(2/3) + BH4/3. Here A and B are intrinsic parameters of the cooling material and H-0 is an extrinsic parameter determined by the purity and homogeneity of the sample. This theoretical prediction is confirmed by measurements on variously pure poly- and single-crystalline samples of Gd. The Curie point of pure Gd is found to be 295(1) K; however, the maximum of -Delta S-M is attained at a lower temperature: The higher the quality of the sample, the closer the peak position to 295 K. Further tests are reported for a series of melt-spun LaFe13-xSix alloys. These are found to follow the same field dependence, despite the fact that for certain compositions (x < 1.8) they experience a phase transition of first, rather than second, order.

URL<Go to ISI>://000286740800001
Alternate JournalPhys. Rev. B