- Curie temperatures and modified de Gennes factors of rare earth nitrides
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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.
- Hirayama, Yusuke,Nakagawa, Takashi,Yamamoto, Takao A.
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- The Formation of Solid Solutions Between ThN and LaN, CeN, PrN, SmN, GdN and ErN
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X-Ray studies of the mixed nitride phases indicate complete solid solubility in all case. - Keywords: Nitrides; Rare earth nitrides; Thorium nitride
- Ettmayer, Peter,Waldhart, Johann,Vendl, Alfred,Banik, Gerhard
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- Magnetocaloric effects of ferromagnetic erbium mononitride
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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.
- Nakagawa, Takashi,Arakawa, Takayuki,Sako, Kengo,Tomioka, Naoto,Yamamoto, Takao A.,Kusunose, Takafumi,Niihara, Koichi,Kamiya, Koji,Numazawa, Takenori
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- Magnetic properties of ErN films
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We report a magnetization study of stoichiometric ErN nanocrystalline films grown on Si and protected by a GaN passivating layer. According to the temperature dependence of the resistivity the films are heavily doped semiconductors. Above 100 K the magnetization data fit well to a Curie-Weiss behavior with a moment expected within the free-ion Er3 +J = frac(15, 2) multiplet. Below 50 K the Curie-Weiss plot steepens to an effective moment corresponding to that in the crystal-field determined quartet ground state, and develops a clear paramagnetic Curie-Weiss temperature of about 4.5 K. Zero-field- and field-cooled magnetization curves and the AC susceptibility firmly establish a ferromagnetic ground state within that multiplet below a Curie temperature of 6.3 ± 0.7 K. Due to the (1 1 1) texture of the film the comparison between the magnetization behavior, when the field is applied parallel and perpendicular to the film plane, gives new information about the magnetic structure. An arrangement of the moments according to the model derived from neutron diffraction for bulk HoN is strongly suggested.
- Meyer,Ruck,Preston,Granville,Williams,Trodahl
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