14 research outputs found
Consistent model of magnetism in ferropnictides
The discovery of superconductivity in LaFeAsO introduced the ferropnictides
as a major new class of superconducting compounds with critical temperatures
second only to cuprates. The presence of magnetic iron makes ferropnictides
radically different from cuprates. Antiferromagnetism of the parent compounds
strongly suggests that superconductivity and magnetism are closely related.
However, the character of magnetic interactions and spin fluctuations in
ferropnictides, in spite of vigorous efforts, has until now resisted
understanding within any conventional model of magnetism. Here we show that the
most puzzling features can be naturally reconciled within a rather simple
effective spin model with biquadratic interactions, which is consistent with
electronic structure calculations. By going beyond the Heisenberg model, this
description explains numerous experimentally observed properties, including the
peculiarities of the spin wave spectrum, thin domain walls, crossover from
first to second order phase transition under doping in some compounds, and
offers new insight in the occurrence of the nematic phase above the
antiferromagnetic phase transition.Comment: 5 pages, 3 figures, revtex
Magnetic circular dichroism in L3M2,3M2,3 Auger emission from Fe and Co metals due to symmetry-breaking interactions
Pressure-induced collapse of the spin-orbital Mott state in the hyperhoneycomb iridate β-Li2IrO3
Possible origin of linear magnetoresistance: Observation of Dirac surface states in layered PtBi2
The nonmagnetic compounds showing extremely large magnetoresistance are attracting a great deal of research interest due to their potential applications in the field of spintronics. PtBi2 is one of such interesting compounds showing large linear magnetoresistance (MR) in both the hexagonal and pyrite crystal structure. We use angle-resolved photoelectron spectroscopy and density functional theory calculations to understand the mechanism of liner MR observed in the layered PtBi2. Our results uncover linear dispersive surface Dirac states at the (Gamma) over bar point, crossing the Fermi level with a node at a binding energy of approximate to 900 meV, in addition to the previously reported Dirac states at the (K) over bar point in the same compound. We further notice from our dichroic measurements that these surface states show an asymmetric spectral intensity when measured with left and right circularly polarized light, hinting at a substantial spin polarization of the bands. Following these observations, we suggest that the linear dispersive Dirac states at the (Gamma) over bar and (K) over bar points are likely to play a crucial role for the linear field dependent magnetoresistance recorded in this compound