JOSE MESTNIK FILHO
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Artigo IPEN-doc 22670 Magnetic hyperfine interactions on Cd sites of the rare-earth cadmium compounds RCd (R=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er)2016 - CAVALCANTE, F.H.M.; LEITE NETO, O.F.L.S.; SAITOVITCH, H.; CAVALCANTE, T.P.D.; CARBONARI, A.W.; SAXENA, R.N.; BOSCH-SANTOS, B.; PEREIRA, L.F.D.; MESTNIK-FILHO, J.; FORKER, M.This paper reports the investigation of the magnetic hyperfine field Bhf in a series of rare-earth (R) cadmium intermetallic compounds RCd and GdCd2 measured by perturbed angular correlation (PAC) spectroscopy using 111In/111Cd as probe nuclei at Cd sites as well as first-principles calculations of Bhf at Cd sites in the studied compounds. Vapor–solid state reaction of R metals with Cd vapor and the 111In radioisotope was found to be an appropriate route of doping rare-earth cadmium compounds with the PAC probe 111In/111Cd. The observation that the hyperfine parameters depend on details of the sample preparation provides information on the phase preference of diffusing 111In in the rare-earth cadmium phase system. The 111Cd hyperfine field has been determined in the compounds RCd for the R constituents Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, in several cases as a function of temperature. For most R constituents, the temperature dependence Bhf (T ) of 111Cd:RCd is consistent with ferromagnetic order of the compound. DyCd, however, presents a remarkable anomaly: a finite magnetic hyperfine field is observed only in the temperature interval 35 K T 80 K which indicates a transition from ferromagnetic order to a spin arrangement where all 4f -induced contributions to the magnetic hyperfine field at the Cd site cancel. First-principles calculation results for DyCd show that the (π, π, 0) antiferromagnetic configuration is energetically more favorable than the ferromagnetic. The approach used in the calculations to simulate the RCd system successfully reproduces the experimental values of Bhf at Cd sites and shows that the main contribution to Bhf comes from the valence electron polarization. The de Gennes plot of the hyperfine field Bhf of 111Cd:RCd vs the 4f -spin projection (g − 1)J reflects a decrease of the strength of indirect 4f -4f exchange across the R series. Possible mechanisms are discussed and the experimental results indicate that the indirect coupling is provided by the intra-atomic 4f -5d exchange and interatomic 5d-5d interaction between the spin-polarized 5d electrons of neighboring R atoms. The ratio of the hyperfine fields of GdCd and GdCd2 scales with the number of nearest Gd neighbors. In the paramagnetic phases of the RCd compounds, the PAC spectra indicate the presence of a broad distribution of weak quadrupole interactions suggesting a perturbation of the cubic CsCl symmetry of the Cd site, most probably due to chemical disorder of the R and Cd sublattices. A substantial interchange of R and Cd atoms is also reflected in the temperature dependence of the linewidth of the magnetic hyperfine interaction in the magnetically ordered phase of RCd and GdCd2. Its critical increase towards the order temperature is evidence for a distribution of the order temperature with a width of about 10 K.Artigo IPEN-doc 21733 A method to determine contributions to the hyperfine field at Ce probes in magnetic host: Application to Ce impurities at RE sites in REAg (RE=Gd, Tb, Dy, Ho) compounds2016 - CAVALCANTE, F.H.M.; PEREIRA, L.F.D.; CARBONARI, A.W.; MESTNIK-FILHO, J.; SAXENA, R.N.Artigo IPEN-doc 21223 Charge distribution and hyperfine interactions in the vicinity of impurity sites in Insub(2)Osub(3) doped with Fe, Co and Ni2015 - SENA, C.; COSTA, M.S.; MUNOZ, E.L.; CABRERA PASCA, G.A.; PEREIRA, L.F.D.; MESTNIK FILHO, J.; CARBONARI, A.W.; COAQUIRA, J.A.H.Artigo IPEN-doc 10576 Study of magnetism in GDTIN(T=NI,PD,CU) compounds by perturbed gamma-gamma angular correlation spectroscopy2005 - LEITE, D.M.T.; LAPOLLI, A.L.; CARBONARI, A.W.; SAXENA, R.N.; MESTNIK FILHO, J.Artigo IPEN-doc 10586 Determinacao do campo hiperfino magnetico em nucleos de sup(148)Ce substituindo Gd em GdAg por electroscopia de correlacao angular perturbada2005 - PEREIRA, L.F.D.; MESTNIK FILHO, J.; CAVALCANTE, F.H.M.; CARBONARI, A.W.Artigo IPEN-doc 16267 Magnetic field at sup(140)Ce in Dy sites in DyX (X=Cu, Ag) compounds studied by perturbed angular correlation spectroscopy2007 - CARBONARI, A.W.; CAVALCANTE, F.H.M.; PEREIRA, L.F.D.; CABRERA PASCA, G.A.; MESTNIK FILHO, J.; SAXENA, R.N.Artigo IPEN-doc 10786 Investigation of the local magnetism at rare-earth sites in RAg(R=rare-earth) intermetallic compounds using perturbed gamma-gamma angular correlation spectroscopy2005 - CAVALCANTE, F.H.M.; CARBONARI, A.W.; MESTNIK FILHO, J.; PEREIRA, L.F.D.; SAXENA, R.N.; OLIVEIRA, A.J.A.; SOUZA, P.E.N.; SANTOS, A.O.Time differential perturbed gamma-gamma angular correlation (TDPAC) technique was used to measure the magnetic hyperfine field (mhf) at rare earth sites in intermetallic compounds RAg (R = Dy, Gd, Ho, Nd, Tb) in order to study the behavior of the mhf with 4f-electron density variation. 140Ce was used as probe nuclei in the TDPAC measurements, which was carried out in the temperature range of 10 K to 300 K. The results of the temperature dependence of the mhf show a standard antiferromagnetic behavior below the magnetic order temperature but, for lower temperatures, it was observed a sharp deviation from the expected Brillouin-like behavior with an increase of the mhf values. The values of the mhf for each compound at the lowest temperature just above the deviation were compared to the respective projection of the rare-earth spin on the total angular momentum J. The results showed to follow a similar behavior when compared to those for the magnetic moment of the compounds.Artigo IPEN-doc 10571 Perturbed angular correlation gamma-gamma spectroscopy with sup(140)Ce isotope in CeMnsub(2)Gesub(2)2005 - MESTNIK FILHO, J.; CARBONARI, A.W.; LALIC, M.V.Artigo IPEN-doc 11957 Study of the magnetic hyperfine field acting on sup(140)Ce probes in NdAg by TDPAC spectroscopy and AB-initio eletronic structure calculations2007 - PEREIRA, LUCIANO F.D.; MESTNIK FILHO, JOSE; CAVALCANTE, FABIO H. de M.; CARBONARI, ARTUR W.; MERCURIO, MARCIO E.; CORDEIRO, MOACIR R.; MALAVASI, RODOLFO F.L.; PASCA, GABRIEL A.C.; SAXENA, RAJENDRA N.Artigo IPEN-doc 10274 Magnetic hyperfine fields on sup(140)Ce probes substituting for the rare earth in RCosub(2) laves phases2003 - SAITOVITCH, H.; SILVA, P.R.J.; CARBONARI, A.W.; MESTNIK FILHO, J.; LALIC, M.V.
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