arXiv subjects

C. Adriano

Publications and source records attributed to C. Adriano.

59 records · Page 4Linked to original sources

arXiv2011

The magnetic structures of the anisotropic inter-metallic compounds Er$_2$CoGa$_8$ and Tm$_2$CoGa$_8$

Two members of the iso-structural R$_2$CoGa$_8$ inter-metallic series, Er$_2$CoGa$_8$ and Tm$_2$CoGa$_8$, have been studied by powder neutron diffraction. Antiferromagnetic ordering of the rare-earth sublattices was confirmed to occur at 3.0 K and 2.0 K, respectively. Furthermore, determination of the critical exponent showed Er$_2$CoGa$_8$ to adopt a 3D universality class. In spite of a common magnetic easy axis and similar structural characteristics, the antiferromagnetic structures were found to be different for the erbium and thulium based compounds. The corresponding magnetic space groups were determined to be $P_{2a}mmm'$ and $P_Cmmm$. The difference in magnetic structures is discussed based on crystal electric field effects that are known to be prevalent in such materials.

cond-mat.str-el↗

arXiv2010

Distinct high-T transitions in underdoped Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$

In contrast to the simultaneous structural and magnetic first order phase transition $T_{0}$ previously reported, our detailed investigation on an underdoped Ba$_{0.84}$K$_{0.16}$Fe$_{2}$As$_{2}$ single crystal unambiguously revealed that the transitions are not concomitant. The tetragonal ($τ$: I4/mmm) - orthorhombic ($\vartheta$: Fmmm) structural transition occurs at $T_{S}\simeq$ 110 K, followed by an adjacent antiferromagnetic (AFM) transition at $T_{N}\simeq$ 102 K. Hysteresis and coexistence of the $τ$ and $\vartheta$ phases over a finite temperature range observed in our NMR experiments confirm the first order character of the structural transition and provide evidence that both $T_{S}$ and $T_{N}$ are strongly correlated. Our data also show that superconductivity (SC) develops in the $\vartheta$ phase below $T_{c}$ = 20 K and coexists with long range AFM. This new observation, $T_{S}\neq T_{N}$, firmly establishes another similarity between the hole-doped BaFe$_{2}$As$_{2}$ via K substitution and the electron-doped iron-arsenide superconductors.

cond-mat.supr-con↗

arXiv2009

Cd-doping effects in Ce2MIn8 (M = Rh and Ir) heavy fermion compounds

Low temperature magnetic properties of Cd-doped Ce2MIn8 (M = Rh and Ir) single crystals are investigated. Experiments of temperature dependent magnetic susceptibility, heat capacity and electrical resistivity measurements revealed that Cd-doping enhances the antiferromagnetic (AFM) ordering temperature from TN = 2.8 K (x = 0) to TN = 4.8 K (x = 0.21) for Ce2RhIn8-xCdx and induces long range AFM ordering with TN = 3.8 K (x = 0.21) for Ce2IrIn8-xCdx. Additionally, X-ray and neutron magnetic scattering studies showed that Cd-doped samples present below TN a commensurate antiferromagnetic structure with a propagation vector (1/2,1/2,0). The resolved magnetic structures for both compounds indicate that the Cd-doping tends to rotate the direction of the ordered magnetic moments toward the ab-plane. This result suggests that the Cd-doping affects the Ce3+ ground state single ion anisotropy modifying the crystalline electrical field (CEF) parameters at the Ce3+ site. Indications of CEF evolution induced by Cd-doping were also found in the electrical resistivity measurements. Comparisons between our results and the general effects of Cd-doping on the related compounds CeMIn5 (M = Co, Rh and Ir) confirms the claims that the Cd-doping induced electronic tuning is the main effect favoring AFM ordering in these compounds.

cond-mat.str-el↗

arXiv2008

La-dilution effects in TbRhIn5 antiferromagnet

We report measurements of temperature dependent magnetic susceptibility, resonant x-ray magnetic scattering (XRMS) and heat capacity on single crystals of Tb1-xLaxRhIn5 for nominal concentrations in the range 0.0 < x < 1.0. TbRhIn5 is an antiferromagnetic (AFM) compound with TN ~ 46 K, which is the highest TN values along the RRhIn5 series. We explore the suppression of the antiferromagnetic (AFM) state as a function of La-doping considering the effects of La-induced dilution and perturbations to the tetragonal crystalline electrical field (CEF) on the long range magnetic interaction between the Tb$^{3+}$ ions. Additionally, we also discuss the role of disorder. Our results and analysis are compared to the properties of the undoped compound and of other members of the RRhIn5 family and structurally related compounds (R2RhIn8 and RIn3). The XRMS measurements reveal that the commensurate magnetic structure with the magnetic wave-vector (0,1/2,1/2) observed for the undoped compound is robust against doping perturbations in Tb0.6La0.4RhIn5 compound.

cond-mat.other↗

arXiv2007

Magnetic structure of Sm2IrIn8

The magnetic structure of the intermetallic antiferromagnet Sm2IrIn8 was determined using x-ray resonant magnetic scattering (XRMS). Below TN = 14.2, Sm2IrIn8 has a commensurate antiferromagnetic structure with a propagation vector (1/2,0,0). The Sm magnetic moments lie in the ab plane and are rotated roughly 18 degrees away from the a axis. The magnetic structure of this compound was obtained by measuring the strong dipolar resonant peak whose enhancement was of over two orders of magnitude at the L2 edge. At the L3 edge both quadrupolar and dipolar features were observed in the energy line shape. The magnetic structure and properties of Sm2IrIn8 are found to be consistent with the general trend already seen for the Nd-, Tb- and the Ce-based compounds from the RmMnIn3m+2n family (R = rare earth; M=Rh or Ir, m = 1, 2; n = 0, 1), where the crystalline electrical field (CEF) effects determine the direction of magnetic moments and the TN evolution in the series. The measured Neel temperature for Sm2IrIn8 is slightly suppressed when compared to the TN of the parent cubic compound SmIn3.

cond-mat.str-el↗