Kausik Sengupta

Magnetic behaviour of quasi-one-dimensional oxides, Ca3Co1+xMn1−xO6

Abstract The results of ac and dc magnetization and heat capacity measurements on the oxides, Ca3Co1+xMn1−xO6, forming in a K4CdCl6-derived rhombohedral quasi-one-dimensional crystal structure, are reported. As far as Ca3Co2O6 is concerned, the results reveal a truly complex nature of the two magnetic transitions, identified to set in at 24 and 12 K in the previous literature. However, partial replacement of Co by Mn apparently results in a long magnetic ordering of an antiferromagnetic type (below 13 and 18 K for x=0.0 and 0.25, respectively), instead of spin-glass freezing in spite of the fact that there is Co–Mn disorder; in addition, interestingly there are hysteretic spin reorientation effects as revealed by the isothermal magnetization behavior.

Field-induced first-order magnetic phase transition in an intermetallic compound Nd7Rh3 : Evidence for kinetic hindrance, phase coexistence, and percolative electrical conduction

The compound, Nd7Rh3, crystallizing in Th7Fe3-type hexagonal structure, was previously known to exhibit two magnetic transitions, one at 32 K and the other at 10 K (in zero magnetic field). Here, we report the existence of a field-induced first-order antiferromagnetic to ferromagnetic transition at 1.8 K in this compound. On the basis of the measurements of isothermal magnetization and magnetoresistance, we provide evidence for the occurence of kinetic-hindrance, proposed in the literature, resulting in phase co-existence (super-cooled ferromagnetic + antifferomagnetic) and percolative electrical conduction in this stoichiometric intermetallic compound. A point of emphasis, as inferred from ac susceptibility data, is that such a co-existing phase is different from spin-glasses, thereby clarifying a question raised in the field of phase-separation.

Enhanced electrical resistivity before Néel order in the metals RCuAs2 (R=Sm, Gd, Tb, and Dy).

We report an unusual temperature (T) dependent electrical resistivity (rho) behavior in a class of ternary intermetallic compounds of the type RCuAs2 (R=rare earths). For some rare earths (Sm, Gd, Tb, and Dy) with negligible 4f hybridization, there is a pronounced minimum in rho(T) far above respective Néel temperatures (T(N)). However, for the rare earths which are more prone to exhibit such a rho(T) minimum due to 4f-covalent mixing and the Kondo effect, this minimum is depressed. These findings, difficult to explain within the hitherto-known concepts, present an interesting scenario in magnetism.

Large magnetoresistance and magnetocaloric effect above 70 K in Gd 2 Co 2 Al , Gd 2 Co 2 Ga , and Gd 7 Rh 3

The electrical resistivity, magnetization, and heat-capacity behavior of the Gd-based compounds,

Large magnetoresistance in the magnetically ordered state as well as in the paramagnetic state near 300 K in an intermetallic compound, Gd7Rh3

{\mathrm{Gd}}_{2}{\mathrm{Co}}_{2}\mathrm{Al}

Heavy fermion superconductor CeCu 2 Si 2 under high pressure: Multiprobing the valence crossover

,

Magnetic, electrical resistivity, heat-capacity, and thermopower anomalies in CeCuAs2

{\mathrm{Gd}}_{2}{\mathrm{Co}}_{2}\mathrm{Ga}

Positive and negative pressure effects on the magnetic ordering and the Kondo effect in the compound Ce2RhSi3

, and

Structural and magnetic anomalies among the spin-chain compounds, Ca3Co1+xIr1−xO6

{\mathrm{Gd}}_{7}{\mathrm{Rh}}_{3}

Large magnetoresistance anomalies in Dy7Rh3

, ordering magnetically at