Specific heat and magnetic entropy associated with magnetic ordering in Al-rich RAL<inf>2</inf>sintered compounds

Abstract

Crystallographic and thermo-magnetic measurements have been made on the sintered RAl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> intermetallic compounds, where R = Gd, Tb, Dy, Ho and Er. These Laves phase compounds are important ferromagnetic substances for the Ericsson type magnetic refrigerator in the temperature range above 10 K. The powder metallurgical approach was used to prepare the samples. The sintering characteristics in the R-Al system were clarified in the previous paper. Based on that result, the RAl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.2</inf> system was selected in this investigation. Thermo-magnetic measurements show that Curie temperatures for the RAl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.2</inf> sintered compounds are inclined to be about 2 to 15 K lower than those for stoichiometric compounds. In this paper, specific heat and magnetic entropy values for the above Al-rich RAl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> high density sintered compounds are shown in respect to application to magnetic refrigerants in the above 10 K temperature range. Then, the RAl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> phase contribution in RAl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.2</inf> sintered compounds to magnetic entropy and its magnetic properties are discussed.