Exchange Coupling in GdM Compounds

K.H.J. Buschowa, G.E. Grechnevb, A. Hjelmc, Y. Kasamatsud, A.S. Panfilovb and I.V. Svechkarevb aVan der Waals-Zeeman Institute, University of Amsterdam Valckenierstraat 65, 1018 XE Amsterdam, The Netherlands bB. Verkin Institute for Low Temperature Physics, Kharkov, 310164, Ukraine cHelax AB, Box 1704, 751 47 Uppsala, Sweden dKure National College of Technology, 2-2-11 Agaminami, Kure 737, Japan

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The magnetic susceptibility of ferromagnetic GdM alloys (M=Cu1-xGax, Mg, Zn) has been investigated under helium gas pressure for temperatures above TC. The evaluated pressure derivatives of the paramagnetic Curie temperature, dlnΘ/dP, appeared to be remarkably different for isovalent GdMg and GdZn compounds (-11.2 and -0.1 Mbar-1, respectively). An analysis of the obtained dlnΘ/dP values for GdCu1-xGax alloys and results of ab initio electronic structure calculations have revealed the essential role of 5d electrons as the mediators of exchange coupling in ferromagnetic GdM compounds. The pressure derivatives of TC were calculated by employing the modern mean-field theory, as well as the spin-fluctuation model. As a result, good agreement is found with the experimental values of dlnΘ/dP.

DOI: 10.12693/APhysPolA.92.267 PACS numbers: 75.10.Lp, 75.20.En