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TbNiGe 2 compound crystallizes in the CeNiSi 2 type orthorhombic crystal structure and shows antiferromagnetic ordering below 39 K. Magnetization isotherms show linear dependence for field up to 50 kOe. It shows inverse magnetocaloric effect, which is attributed to antiferromagnetic interactions between the moments. The resistivity data was fitted in high and low temperature regimes. The low temperature fit confirms the antiferromagnetic ordering, while the high temperature data follow Bloch-Grüneisen-Mott relation. Ab initio LSDA + U calculations show no spin polarization from Ni 3d electronic states and reproduce the antiferromagnetic long-range ordering of the Tb magnetic moments and their values in good agreement with the previous neutron diffraction data. Optical conductivity data supports the electronic structure calculations and show that it is mostly provided by the transitions involving Ni 3d and Tb 4f electronic states. [ABSTRACT FROM AUTHOR]

A number of experiments have been performed to study magnetic, electronic and optical properties of HoNiSi, along with theoretical calculations. The compound crystallizes in orthorhombic crystal structure and orders antiferromagnetically at T N = 4.6 K. Magnetization isotherms show curvature in low fields, revealing a field induced metamagnetic transition. Application of field reduces the resistivity near T N , which results in a large negative MR. The maximum value of MR has been found to be −24% at 4 K for 50 kOe. Strong antiferromagnetic interactions among the moments below 4 K result in positive MR, which changes with field. The antiferromagnetic ordering with the effective magnetic moments of Ho close to the observed value is obtained in the LSDA + U calculations accounting for the electronic correlations in the 4f Ho shell. In the experimental optical conductivity interband transitions involving 4f Ho and 5d Ho forms the main features in good agreement with the theoretical electronic structure of HoNiSi. [ABSTRACT FROM AUTHOR]

RRhGe (R = Tb, Dy, Er, Tm) compounds have been studied by different experimental probes and theoretical ab initio calculations. These compounds show very interesting magnetic and transport properties. All the compounds are antiferromagnetic with some of them showing spin-reorientation transition at low temperatures. The magnetocaloric effect estimated from magnetization data shows high values in all these compounds. Magnetoresistance is negative near the ordering temperatures and positive at low temperatures. The electronic structure calculations accounting for electronic correlations in the 4f rare-earth shell reveal the closeness of the antiferromagnetic ground state and other types of magnetic orderings in the rare-earth sublattice. These calculations are also in agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Polycrystalline HoSn 1.1 Ge 0.9 and DySn 1.1 Ge 0.9 compounds have been studied by means of different experimental probes. Both the compounds are antiferromagnetic and show metamagnetic transition at low temperatures. HoSn 1.1 Ge 0.9 shows a sign change in magnetocaloric effect (MCE) and magnetoresistance (MR) with field, which is attributed to the metamagnetic transition. DySn 1.1 Ge 0.9 shows characteristics of a typical antiferromagnet, as evidenced by magnetization, MCE and MR data. 119 Sn Mössbauer studies show hyperfine splitting at low temperatures, consistent with magnetization data. Thermoelectric power and resistivity measurements reveal metallic behavior in these compounds. Magnetic, magnetocaloric and the magnetoresistance data clearly show that the antiferromagnetic coupling in DySn 1.1 Ge 0.9 is stronger than in HoSn 1.1 Ge 0.9 . [ABSTRACT FROM AUTHOR]

RTX ( R = rare earths, T = 3 d /4 d /5 d , transition metals such as Sc, Ti, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, and X = p -block elements such as Al, Ga, In, Si, Ge, Sn, As, Sb, Bi) series is a huge family of intermetallics compounds. These compounds crystallize in different crystal structures depending on the constituents. Though these compounds have been known for a long time, they came to limelight recently in view of the large magnetocaloric effect (MCE) and magnetoresistance (MR) shown by many of them. Most of these compounds crystallize in hexagonal, orthorhombic and tetragonal crystal structures. Some of them show crystal structure modification with annealing temperature; while a few of them show iso-structural transition in the paramagnetic regime. Their magnetic ordering temperatures vary from very low temperatures to temperatures well above room temperature (∼510 K). Depending on the crystal structure, they show a variety of magnetic and electrical properties. These compounds have been characterized by means of a variety of techniques/measurements such as X-ray diffraction, neutron diffraction, magnetic properties, heat capacity, magnetocaloric properties, electrical resistivity, magnetoresistance, thermoelectric power, thermal expansion, Hall effect, optical properties, XPS, Mössbauer spectroscopy, ESR, μSR, NMR, and NQR. Some amount of work on theoretical calculations on electronic structure, crystal field interaction and exchange interactions has also been reported. The interesting aspect of this series is that they show a variety of physical properties such as Kondo effect, heavy fermion behavior, spin glass state, intermediate valence, superconductivity, multiple magnetic transitions, metamagnetism, large MCE, large positive as well as negative MR, spin orbital compensation, magnetic polaronic behavior, and pseudo gap effect. Except Mn, no other transition metal in these compounds possesses considerable magnetic moments. Because of this R Mn X compounds in general have high ordering temperatures. Interstitial modification using hydrogen is found to alter their crystal structures and magnetic properties considerably. RTX compounds also show interesting pressure effects on their structural and magnetic properties. In summary, these compounds show variety of physical properties over a wide range of temperatures. This review is intended to cover all the important results obtained in this family, particularly in the last few years. [ABSTRACT FROM AUTHOR]

We present structural, magnetic, thermal, magnetocaloric, and electrical transport properties of polycrystalline GdRhSn. Magnetization data show that it orders antiferromagnetically at TN = 16.2 K. The compound has the ZrNiAl type hexagonal crystal structure at room temperature and undergoes a first order iso-structural transition in the paramagnetic state at 245 K. The unit cell volume change at the transition is small (-0.07%) but discontinuous, in agreement with the first-order nature of the transition observed by magnetic, transport, and heat capacity measurements. The anisotropic changes of the lattice parameters are Δa/a = 0.28% and Δc/c = -0.64% on cooling. A substantial change in the 4f and conduction electron hybridization, giving rise to an increased integrated DOS, occurs when the high temperature phase transforms to the low temperature phase. A moderate magnetocaloric effect at TN (ΔSM = -6.5 J/kg K and ΔTad = 4.5 K for ΔH = 50 kOe) has been measured using both magnetization and heat capacity data. [ABSTRACT FROM AUTHOR]

Highlights: [•] GdRhGe shows two magnetic phase transitions, one collinear while other seems to be complex. [•] The ac susceptibility manifests the complex nature of second magnetic phase transition. [•] The compound shows large positive MR at low temperatures. [•] The sign change in MR and MCE take place below first magnetic phase transition. [ABSTRACT FROM AUTHOR]