arXiv subjects

S. Chikara

Publications and source records attributed to S. Chikara.

23 records · Page 2Linked to original sources

arXiv2005

Thermal and Magnetic Properties of the Spin-Chain Material, Pr3RuO7

We present measurements of the magnetic moment and specific heat of single crystals of the spin-chain insulator, Pr3RuO7. The susceptibility indicates that three-dimensional antiferromagnetic order sets in at TN = 54 K, with spin polarization approximately along the chain direction, but the susceptibility anisotropy above TN indicates that the intrachain interactions are predominantly ferromagnetic while the interchain interactions are antiferromagnetic. This competition presumably gives rise to the observed metamagnetic behavior for applied fields along the polarization direction. The specific heat anomaly at TN is unusually mean-field in shape, with magnitude indicating that the transition involves mostly ordering of the ruthenium moments. A Schottky-like anomaly at low temperature may be due to praesodynium ions ordering in the effective field established at TN.

cond-mat.str-el↗

arXiv2004

From itinerant ferromagnetism to insulating antiferromagnetism: A magnetic and transport study of single crystal SrRu1-xMnxO3

We report results of a magnetic and transport study of SrRu1-xMnxO3, i.e., Mn doped SrRuO3. The Mn doping drives the system from the itinerant ferromagnetic state (TC=165 K for x=0) through a quantum critical point at xc=0.39 to an insulating antiferromagnetic state. The onset of antiferromagnetism is abrupt with a Neel temperature increasing from 205 K for x=0.44 to 250 K for x=0.59. Accompanying this quantum phase transition is a drastic change in resistivity by as much as 8 orders of magnitude as a function of x at low temperatures. The critical composition xc=0.39 sharply separates the two distinct ground states, namely the ferromagnetic metal from the antiferromagnetic insulator.

cond-mat.str-el↗

arXiv2004

Orbitally-driven Behavior: Mott Transition, Quantum Oscillations and Colossal Magnetoresistance in Bilayered Ca3Ru2O7

We report recent transport and thermodynamic experiments over a wide range of temperatures for the Mott-like system Ca3Ru2O7 at high magnetic fields, B, up to 30 T. This work reveals a rich and highly anisotropic phase diagram, where applying B along the a-, b-, and c-axis leads to vastly different behavior. A fully spin-polarized state via a first order metamagnetic transition is obtained for B||a, and colossal magnetoresistance is seen for B||b, and quantum oscillations in the resistivity are observed for B||c, respectively. The interplay of the lattice, orbital and spin degrees of freedom are believed to give rise to this strongly anisotropic behavior.

cond-mat.str-el↗

arXiv2003

High-temperature weak ferromagnetism on the verge of a metallic state: Impact of dilute Sr-doping on BaIrO3

The 5d-electron based BaIrO3 is a nonmetallic weak ferromagnet with a Curie temperature at Tc=175 K. Its largely extended orbitals generate strong electron-lattice coupling, and magnetism and electronic structure are thus critically linked to the lattice degree of freedom. Here we report results of our transport and magnetic study on slightly Sr doped BaIrO3. It is found that dilute Sr-doping drastically suppresses Tc, and instantaneously leads to a nonmetal-metal transition at high temperatures. All results highlight the instability of the ground state and the subtle relation between magnetic ordering and electron mobility. It is clear that BaIrO3 along with very few other systems represents a class of materials where the magnetic and transport properties can effectively be tuned by slight alterations in lattice parameters.

cond-mat.str-el↗

arXiv2003

Field-tuned Collapse of an Orbital Ordered and Spin-polarized State: Colossal Magnetoresistance in Bilayered Ruthenate

Ca3Ru2O7 with a Mott-like transition at 48 K features different in-plane anisotropies of magnetization and magnetoresistance. Applying magnetic field along the magnetic easy-axis precipitates a spin-polarized state via a first-order metamagnetic transition, but does not lead to a full suppression of the Mott state, whereas applying magnetic field along the magnetic hard axis does, causing a resistivity reduction of three orders of magnitude. The colossal magnetoresistivity is attributed to the collapse of the orbital ordered and spin-polarized state. Evidence for a density wave is also presented.

cond-mat.str-el↗