L. Mendonça Ferreira

Physical properties of disordered double-perovskite Ca2−xLaxFeIrO6

In this work we have synthesized polycrystalline samples for the series of double-perovskite Ca2−xLaxFeIrO6. Their structural and magnetic properties were investigated using experiments of magnetic susceptibility and x-ray powder diffraction. The Ca2−xLaxFeIrO6 compounds form in a monoclinic structure, space group P21∕n, with the presence of significant Fe∕Ir cationic disorder. Interestingly, our results indicate a change in the nature of the microscopic magnetic interaction induced by La doping, where the system seems to evolve from antiferromagnetic in the extremities of the series, x=0 (TN≈75K) and x=2.0, to ferrimagnetic in intermediate regions of the series. However, due to significant presence of disorder and strong competition between ferromagnetic and antiferromagnetic interactions, the saturation of the magnetization was not found to be larger than 0.1μB∕Fe.

Crystal structure and physical properties of Gd3Co4Sn13 intermetallic antiferromagnet

We have synthesized single crystalline samples of Gd3Co4Sn13 intermetallic compound using a Sn-flux method. This compound crystallizes with a cubic Yb3Co4Sn13-type structure, space group Pm-3n, which has 40 atoms per unit cell. Measurements of the magnetic susceptibility, heat capacity, electrical resistivity, and electron spin resonance (ESR) revealed that Gd3Co4Sn13 is a metallic Curie-Weiss paramagnet at high temperature and presents an antiferromagnetic ordering below TN=14.5K. In the paramagnetic state, a single Gd3+ ESR line with a nearly temperature independent g∼2.005(2) is observed, and its linewidth follows a Korringa-like behavior as a function of temperature. From the Korringa rate (ΔH∕ΔT∼4Oe∕K) and g-shift (Δg∼0.012) obtained from the ESR experiments combined with the magnetic susceptibility and specific heat data for Gd3Co4Sn13, we have extracted the exchange parameters between the Gd3+ local moments and the conduction-electrons (c-e) in this compound. This exchange parameter Jfs≈10meV was f...

Structurally tuned magnetic properties of TbmRhnIn3m+2n (m = 1,2; n = 0,1) intermetallic antiferromagnets

We report the evolution of the magnetic properties of a new series of intermetallic compounds TbmRhnIn3m+2nTbmRhnIn3m+2n(m=1,2;n=0,1(m=1,2;n=0,1) which are structurally related to a class of Ce-based heavy-fermion superconductors (HFS). Measurements of temperature-dependent magnetic susceptibility, specific heat and X-ray resonant magnetic scattering (XRMS) were performed on single crystalline samples of TbIn3TbIn3, TbRhIn5TbRhIn5 and Tb2RhIn8Tb2RhIn8. The tetragonal materials TbRhIn5TbRhIn5 and Tb2RhIn8Tb2RhIn8 both order antiferromagnetically with higher ordering temperatures (TN=45.5TN=45.5 and 42.8K, respectively) than their cubic relative TbIn3(TN=32.7K). Their commensurate magnetic structure and the direction of Tb magnetic moments will be discussed in terms of crystalline electrical field (CEF) effects and Ruderman–Kittel–Kasuya–Yoshida (RKKY) interaction with effects of magnetic frustration being released by lower dimensionality. A more general picture about the role of CEF in determining the magnetic properties of other R-based members of these series is discussed.

Structurally tuned magnetic properties of TbmRhnIn3m+2nTbmRhnIn3m+2n (m=1,2m=1,2; n=0,1n=0,1) intermetallic antiferromagnets

We report the evolution of the magnetic properties of a new series of intermetallic compounds TbmRhnIn3m+2nTbmRhnIn3m+2n(m=1,2;n=0,1(m=1,2;n=0,1) which are structurally related to a class of Ce-based heavy-fermion superconductors (HFS). Measurements of temperature-dependent magnetic susceptibility, specific heat and X-ray resonant magnetic scattering (XRMS) were performed on single crystalline samples of TbIn3TbIn3, TbRhIn5TbRhIn5 and Tb2RhIn8Tb2RhIn8. The tetragonal materials TbRhIn5TbRhIn5 and Tb2RhIn8Tb2RhIn8 both order antiferromagnetically with higher ordering temperatures (TN=45.5TN=45.5 and 42.8K, respectively) than their cubic relative TbIn3(TN=32.7K). Their commensurate magnetic structure and the direction of Tb magnetic moments will be discussed in terms of crystalline electrical field (CEF) effects and Ruderman–Kittel–Kasuya–Yoshida (RKKY) interaction with effects of magnetic frustration being released by lower dimensionality. A more general picture about the role of CEF in determining the magnetic properties of other R-based members of these series is discussed.

Structurally tuned magnetic properties of (; ) intermetallic antiferromagnets

We report the evolution of the magnetic properties of a new series of intermetallic compounds TbmRhnIn3m+2nTbmRhnIn3m+2n(m=1,2;n=0,1(m=1,2;n=0,1) which are structurally related to a class of Ce-based heavy-fermion superconductors (HFS). Measurements of temperature-dependent magnetic susceptibility, specific heat and X-ray resonant magnetic scattering (XRMS) were performed on single crystalline samples of TbIn3TbIn3, TbRhIn5TbRhIn5 and Tb2RhIn8Tb2RhIn8. The tetragonal materials TbRhIn5TbRhIn5 and Tb2RhIn8Tb2RhIn8 both order antiferromagnetically with higher ordering temperatures (TN=45.5TN=45.5 and 42.8K, respectively) than their cubic relative TbIn3(TN=32.7K). Their commensurate magnetic structure and the direction of Tb magnetic moments will be discussed in terms of crystalline electrical field (CEF) effects and Ruderman–Kittel–Kasuya–Yoshida (RKKY) interaction with effects of magnetic frustration being released by lower dimensionality. A more general picture about the role of CEF in determining the magnetic properties of other R-based members of these series is discussed.