Magnetic Characteristics of Gadolinium, Praseodymium, and Thulium Nitrides

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Abstract
Bulk magnetic measurements were made on GdN, PrN, and TmN over the range 4.2° to 300°K. GdN is ferromagnetic with Tc = 69°K and a saturation moment of 7.03 μB (gJ = 7.00). Results obtained in the paramagnetic region give: for GdN μeff = 7.86 μB {g[J(J+1)]½ = 7.94}, Θp = 75°K; for PrN 3.57 μB (3.58), −11°K; for TmN 7.32 μB (7.56), −21°K. These nitrides all occur in the NaCl structure. Under the influence of the cubic crystal field the 2J+1-fold degenerate multiplet is decomposed so that Pr and Tm have singlet (nonmagnetic) ground states. Thus if the crystal field splitting exceeds the exchange interaction, no cooperative magnetic phase is expected at low temperatures. The measurements indicate this to be the case for TmN, supporting recent neutron diffraction work, and apparently this is also true for PrN. The possibility cannot be excluded, however, the PrN is a weak ferromagnet. If so, its saturation moment is estimated as 0.27 μB (gJ = 3.2 μB), indicating considerable crystal field quenching of the orbital contribution to the moment.