Heat capacities of Laves phase compounds RMn2 (R = Y, Gd and Er)

Okamoto, Tetsuhiko; Nagata, H.; Fujii, H.; Makihara, Y.

doi:10.1016/0304-8853(87)90382-9

Cited by 36 publications

(12 citation statements)

References 5 publications

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“…However, in the paramagnetic region, there is an anomalous contribution to C p in YMn 12 that cannot be explained from Monte Carlo simulations within this localized Ising model. This contribution could be attributed to the itinerant magnetic character of the 3d electrons in this material, and the development of spin fluctuations above T N , as has been observed in the YMn 2 compound [26]. According to Moriya's theory [27] on spin fluctuations for itinerant magnetic materials, additional contributions to C p would be expected due to an enhancement of spin fluctuations with a wavevector near the propagation vector k = (1, 0, 0) associated with the AF ordering below T N = 110 K exhibited by YMn 12 .…”

Section: Analysis Of the Magnetic Ordering Of The 3d Sublattice: Mont...supporting

confidence: 54%

Heat capacity of RFe_xMn_12−x(R = Gd, Tb and Dy) compounds: wiping out a cooperative 4f–4f exchange interaction by breaking the 3d–4f magnetic symmetry

Piqué¹,

Blanco²,

Burriel³

et al. 2008

J. Phys.: Condens. Matter

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Using adiabatic calorimetry the heat capacity of a series of RFe x Mn 12−x (R = Gd, Tb and Dy) compounds has been measured from 3 to 350 K. The substitution of Fe for Mn in RFe x Mn 12−x influences both the magnetic interactions on the 3d sublattice and the magnetism of R (the Néel temperature doubles on going from x = 0 to 6 and the compounds become ferromagnetic for x = 8 with Curie temperatures of around 300 K). In pure TbMn 12 the heat-capacity data shows a λ-type anomaly associated with the independent cooperative magnetic ordering of the R sublattice (∼5 K), while the anomaly related to the Mn magnetic ordering (∼100 K) is rather smooth, as observed in other itinerant magnetic systems such as YMn 12 . In contrast, the substitution of Fe for Mn leads, on the one hand, to a more localized magnetic behaviour of the 3d sublattice, and, on the other, to magnetic polarization effects between the 3d and 4f sublattices, together with the disappearance of the cooperative magnetic ordering of the R sublattice due to the breaking of the antiferromagnetic symmetry in the 3d sublattice. This is reflected in the heat-capacity curve through a smooth Schottky-like anomaly. In the case of Gd compounds the magnitude of the exchange molecular-field parameter has been deduced by fitting the magnetic contribution to the heat capacity within a simple mean-field model. From this analysis we found that this molecular field acting on the rare-earth site increases with the iron concentration, reaching values as large as 48 T for the concentration x = 6. A similar analysis of the heat capacity in the ordered phase on the Tb compounds also leads to an enhancement of the molecular field with increasing Fe content. These results allow checking the possible crystal-field parameters for these RFe x Mn 12−x compounds.

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Section: Analysis Of the Magnetic Ordering Of The 3d Sublattice: Mont...supporting

confidence: 54%

Heat capacity of RFe_xMn_12−x(R = Gd, Tb and Dy) compounds: wiping out a cooperative 4f–4f exchange interaction by breaking the 3d–4f magnetic symmetry

Piqué¹,

Blanco²,

Burriel³

et al. 2008

J. Phys.: Condens. Matter

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“…Moreover they concluded an ordering of the Gd sublattice below T c (about 35 K). The separate ordering of the Gd sublattice was not confirmed by Mössbauer, NMR and specific heat measurements [10][11][12]. Przewoźnik [10] and Żukrowski [13] concluded from Mössbauer measurements the ordering of the Gd sublattice also above 40 K even up to T N .…”

Section: Introductionmentioning

confidence: 91%

Magnetism of manganese in and (R = Y, Gd, Er) intermetallics

Talik

Neumann

Mydlarz

et al. 1998

J. Phys.: Condens. Matter

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The XPS electronic structure was measured for , and single crystals and pure Mn. Exchange splitting of Mn 3d and 3s states was found for the compounds with magnetic manganese. The electrical resistivity of the single crystal shows an antiferromagnetic transition at 108 K and the second transition at 32 K. The lattice parameter against temperature of exhibits a large spontaneous magnetostriction at . The anisotropic character of the magnetization was found. The results were discussed using the Yamada and Shimizu model.

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“…This totally rules out long-range antiferromagnetism as a possible mechanism for the cusp in the susceptibility of these alloys. On the other hand an appreciable anomaly in the heat capacity occurs at the antiferromagnetic transition of YMn [24]. Since analogous, non-magnetic compounds are not known, it has not been possible for us to separate out the magnetic contribution to the heat capacity in ThMnAl and ThMnIn by subtracting the background electronic and the phonon contribution to the heat capacity of the non-magnetic reference compounds.…”

Section: Thmnmentioning

confidence: 99%

“…A"65, 50.2 and 35.3 mJ/ mol K in ThMnAl, ThMnIn and YMnAl, respectively. In YMn the corresponding value in the magnetically ordered state is 15 mJ/mol K [24]. Normally, the coe$cient of the linear term in the heat capacity, , is related to the electronic density of states at the Fermi level and for ordinary metallic systems with predominantly s, p electrons at the Fermi level it is typically about a few mJ/mol K. However, for metallic systems containing 3d-atoms, is typically an order of magnitude larger due to the presence of relatively narrow d-bands at the Fermi level.…”

Section: Thmnmentioning

confidence: 99%

Possible sign change of Mn–Mn exchange interaction between ThMnAl and ThMnIn

Manfrinetti¹,

Palenzona²,

Dhar³

et al. 2000

Journal of Magnetism and Magnetic Materials

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Heat capacities of Laves phase compounds RMn2 (R = Y, Gd and Er)

Cited by 36 publications

References 5 publications

Heat capacity of RFe_xMn_12−x(R = Gd, Tb and Dy) compounds: wiping out a cooperative 4f–4f exchange interaction by breaking the 3d–4f magnetic symmetry

Heat capacity of RFe_xMn_12−x(R = Gd, Tb and Dy) compounds: wiping out a cooperative 4f–4f exchange interaction by breaking the 3d–4f magnetic symmetry

Magnetism of manganese in and (R = Y, Gd, Er) intermetallics

Possible sign change of Mn–Mn exchange interaction between ThMnAl and ThMnIn

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Heat capacities of Laves phase compounds RMn2 (R = Y, Gd and Er)

Cited by 36 publications

References 5 publications

Heat capacity of RFexMn12−x(R = Gd, Tb and Dy) compounds: wiping out a cooperative 4f–4f exchange interaction by breaking the 3d–4f magnetic symmetry

Heat capacity of RFexMn12−x(R = Gd, Tb and Dy) compounds: wiping out a cooperative 4f–4f exchange interaction by breaking the 3d–4f magnetic symmetry

Magnetism of manganese in and (R = Y, Gd, Er) intermetallics

Possible sign change of Mn–Mn exchange interaction between ThMnAl and ThMnIn

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Heat capacity of RFe_xMn_12−x(R = Gd, Tb and Dy) compounds: wiping out a cooperative 4f–4f exchange interaction by breaking the 3d–4f magnetic symmetry

Heat capacity of RFe_xMn_12−x(R = Gd, Tb and Dy) compounds: wiping out a cooperative 4f–4f exchange interaction by breaking the 3d–4f magnetic symmetry