Curie temperatures and modified de Gennes factors of rare earth nitrides

Hirayama, Yusuke,Nakagawa, Takashi,Yamamoto, Takao A.

, p. 1602 - 1604 (2011)

The Curie temperatures TC of the nitrides of the rare earths (Gd, Tb, Dy, Ho, and Er), including binary systems, were investigated. T C was found to be approximately proportional to the de Gennes factor, ξ=(g-1)2J(J+1), where g is the Lande? g-factor and J is the total angular momentum quantum number of a trivalent rare earth (RE). This proportionality was significantly improved by introducing a modified de Gennes factor, ξbi. The conventional de Gennes factor ξ indicates the exchange interaction given by the inner product of the effective spin components of ions of the same kind, whereas our modified de Gennes factor ξbi also considers interactions between different kinds of ions and statistical factors calculated on the basis of the binomial distribution. The good proportionality obtained between TC and ξbi indicates that the spin components of RE ions interact with each other. This interaction is considered to be responsible for the ferromagnetism of these nitrides (including binary systems). These considerations were supported by the synthesis of and magnetization measurements on GdxEr1-xN (x=0, 0.25, 0.5, 0.75, 1) samples.

Magnetocaloric effects of ferromagnetic erbium mononitride

Nakagawa, Takashi,Arakawa, Takayuki,Sako, Kengo,Tomioka, Naoto,Yamamoto, Takao A.,Kusunose, Takafumi,Niihara, Koichi,Kamiya, Koji,Numazawa, Takenori

, p. 191 - 195 (2006)

The rare earth mononitride, ErN, has been synthesized by the carbothermic reduction and hot isostatic press methods. The magnetocaloric effect of ErN has been evaluated by calculating the magnetic entropy changes, ΔS, from the magnetization data sets and from the heat capacity measured at various temperatures and applied fields. The two results are in good agreement with each other. The ΔS value of ErN is the highest at 7.5 K and higher than that of ErNi2 reported as the candidate material for the magnetic refrigerant of cryogenic technology. Heat capacity curve against temperature of ErN has a peak at 4.4 K at zero-field. The peak value of the heat capacity of ErN is 507 kJ K-1 m-3. This value is larger than those of Er3Ni used commercially as a magnetic regenerator for the Gifford-McMahon refrigerator. The present results indicate that ErN is a promising material for the magnetic refrigerant and regenerator of cooling systems working above the boiling temperature of helium.

Fitzmaurice, J. C.,Hector, A.,Rowley, A. T.,Parkin, I. P.

, p. 235 - 240 (1994)

Seltenerdnitride des Indiums (R3N)In

Kirchner, M.,Niewa, R.,Schnelle, W.,Wagner, F. R.,Walther, D.,Kniep, R.

, (2008/10/08)

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