High-pressure tuning of valence and magnetic interactions in Eu0.5Yb0.5Ga4

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Pressure-induced changes in valence and magnetic ordering are observed in a Eu0.5Yb0.5Ga4 compound by means of element selective x-ray absorption spectroscopy at Eu and Yb L-3 edges. Concomitant Eu and Yb valence transitions towards a 3+ state, together with an antiferromagnetic to ferromagnetic transition, are observed with applied pressures up to 30 GPa. With the support of density functional theory calculations, we argue that hybridization between (Eu/Yb)-5d and Ga orbitals regulates the valence and magnetic exchange interactions in this system.8524Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)US Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC-02- 06CH11357]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)US Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC-02- 06CH11357

Magnetocaloric effect in the RNi5 (R=Pr, Nd, Gd, Tb, Dy, Ho, Er) series

In this paper, the magnetocaloric effect in the hexagonal intermetallic compounds belonging to the RNi5 series was calculated using a Hamiltonian including the crystalline electrical field, exchange interaction, and the Zeeman effect. Experimental work was performed and the two thermodynamics quantities, namely, isothermal entropy change and adiabatic temperature change were obtained for polycrystalline samples, using heat capacity measurements, and compared to the theoretical predictions.701

The influence of spontaneous and field-induced spin reorientation transitions on the magnetocaloric properties of HoZn and ErZn

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We report a theoretical investigation on the magnetocaloric properties of the cubic CsCl-type HoZn and ErZn compounds. Several anomalies in the magnetocaloric quantities, Delta S(T) and Delta T(S), are observed due to spontaneous and/or field-induced spin reorientation transitions in these compounds. In HoZn, a discontinuity in the isothermal entropy change and in the adiabatic temperature change around T(1) = 23 K is ascribed to the spontaneous reorientation transition. Under a magnetic field variation from 0 up to 2 T in the < 110 > and < 100 > directions, an almost table-like behavior in Delta S(T) is predicted between T(1) and T(SR1). The peak around the ferromagnetic-paramagnetic transition temperature in the magnetocaloric quantities shows a dependence on the direction of the applied field. For mu(0)Delta H = 2 T, it reaches 11.9 J/kg K (magnetic field along the < 111 > direction) and 7.9 J/kg K (magnetic field in the < 100 > direction). In ErZn there is also a dependence of Delta S(T) and Delta T(S) on field direction. From the analysis of the spin reorientations in both compounds we have built spin reorientation diagrams that summarize their temperature and field dependence. Our theoretical approach is based on a model Hamiltonian that includes exchange, crystal field, and quadrupolar interactions. (C) 2011 American Institute of Physics. [doi:10.1063/1.3554725]1096Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

CRYSTAL-FIELD EFFECTS ON THE ELECTRON-SPIN RESONANCE OF RARE-EARTHS IN YPD3 - COMPARISON WITH INELASTIC NEUTRONS SCATTERING EXPERIMENTS

39101025103

ELECTRON-SPIN RESONANCE OF ND3+ IN CERU2 AND THRU2 - A STUDY OF THE SUPERCONDUCTING AND NORMAL STATES

1161249126

GENESIS OF A SOLID FOAM - IRON(III) METAPHOSPHATE TRANSFORMATION IN SOL-GEL CRYSTALLIZATION PROCESSES

651013101

ELECTRON-SPIN-RESONANCE AND LATTICE-PARAMETER STUDY OF CERIUM CUBIC LAVES-PHASE COMPOUNDS - EVIDENCE FOR INTERMEDIATE-VALENCE STATE

45241966197

ELECTRON-SPIN-RESONANCE AND PHOTOACOUSTIC STUDIES OF THE CRYSTALLIZATION OF IRON(III) METAPHOSPHATE

31312212

Investigation of the first-order metamagnetic transitions and the colossal magnetocaloric effect using a Landau expansion applied to MnAs compound

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We have explored a simple Landau model to calculate magnetization isotherms considering magnetic hysteresis. The model parameters have been chosen to fit the magnetic and magnetocaloric data of MnAs compound. Experimental data show that there is a great difference between the isothermal variation of the entropy (S(T)) obtained from isotherms measured increasing and decreasing magnetic field. This great difference is reproduced theoretically. From the experimental and phenomenological isotherms, we calculated the S(T). From the theoretical entropy, we also obtained S(T), which does not present the colossal peak.6816772Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq