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Register a new userEffect of Applied Orthorhombic Lattice Distortion on the Antiferromagnetic Phase of CeAuSb$_2$
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We study the response of the antiferromagnetism of CeAuSb$_2$ to orthorhombic lattice distortion applied through in-plane uniaxial pressure. The response to pressure applied along a $langle 110 rangle$ lattice direction shows a first-order transition at zero pressure, which shows that the magnetic order lifts the $(110)/(1bar{1}0)$ symmetry of the unstressed lattice. Sufficient $langle 100 rangle$ pressure appears to rotate the principal axes of the order from $langle 110 rangle$ to $langle 100 rangle$. At low $langle 100 rangle$ pressure, the transition at $T_N$ is weakly first-order, however it becomes continuous above a threshold $langle 100 rangle$ pressure. We discuss the possibility that this behavior is driven by order parameter fluctuations, with the restoration of a continuous transition a result of reducing the point-group symmetry of the lattice.
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We present results of measurements of resistivity of CAS{} under the combination of $c$-axis magnetic field and in-plane uniaxial stress. In unstressed CAS{} there are two magnetic phases. The low-field A phase is a single-component spin-density wave (SDW), with $mathbf{q} = (eta, pm eta, 1/2)$, and the high-field B phase consists of microscopically coexisting $(eta, eta, 1/2)$ and $(eta, -eta, 1/2)$ spin-density waves. Pressure along a $langle 100 rangle$ lattice direction is a transverse field to both of these phases, and so initially has little effect, however eventually induces new low- and high-field phases in which the principal axes of the SDW components appear to have rotated to the $langle 100 rangle$ directions. Under this strong $langle 100 rangle$ compression, the field evolution of the resistivity is much smoother than at zero strain: In zero strain, there is a strong first-order transition, while under strong $langle 100 rangle$ it becomes much broader. We hypothesize that this is a consequence of the uniaxial stress lifting the degeneracy between the (100) and (010) directions.
We report a field-temperature phase diagram and an entropy map for the heavy fermion compound CeAuSb$_2$. CeAuSb$_2$ orders antiferromagnetically below $T_N=6.6$~K, and has two metamagnetic transitions, at 2.8 and 5.6~T. The locations of the critical endpoints of the metamagnetic transitions, which may play a strong role in the putative quantum criticality of CeAuSb$_2$ and related compounds, are identified. The entropy map reveals an apparent entropy balance with Fermi liquid behavior, implying that above the N{e}el transition the Ce moments are incorporated into the Fermi liquid. High-field data showing that the magnetic behavior is remarkably anisotropic are also reported.
We use neutron scattering to study the lattice and magnetic structure of the layered half-doped manganite Pr$_{0.5}$Ca$_{1.5}$MnO$_4$. On cooling from high temperature, the system first becomes charge- and orbital- ordered (CO/OO) near $T_{CO}=300$ K and then develops checkerboard-like antiferromagnetic (AF) order below $T_{N}=130$ K. At temperatures above $T_{N}$ but below $T_{CO}$ ($T_N<T<T_{CO}$), the appearance of short-range AF spin correlations suppresses the CO/OO induced orthorhombic strain, contrasting with other half-doped manganites, where AF order has no observable effect on the lattice distortion. These results suggest that a strong spin-lattice coupling and the competition between AF exchange and CO/OO ordering ultimately determines the low-temperature properties of the system.
The orthorhombic antiferromagnetic compound CuMnAs was recently predicted to be an antiferromagnetic Dirac semimetal if both the Ry gliding and S2z rotational symmetries are preserved in its magnetic ordered state. In our previous work on Cu0.95MnAs and Cu0.98Mn0.96As, we showed that in their low temperature commensurate antiferromagnetic state the b axis is the magnetic easy axis, which breaks the S2z symmetry. As a result, while the existence of Dirac fermions is no longer protected, the polarized surface state makes this material potentially interesting for antiferromagnetic spintronics. In this paper, we report a detailed study of the anisotropic magnetic properties and magnetoresistance of Cu0.95MnAs and Cu0.98Mn0.96As. Our study shows that in Cu0.95MnAs the b axis is the easy axis and the c axis is the hard axis. Furthermore, it reveals that Cu0.95MnAs features a spin-flop phase transition at high temperatures and low fields when the field is applied along the easy b axis, resulting in canted antiferromagnetism. However, no metamagnetic transition is observed in Cu0.98Mn0.96As, indicating that the magnetic interactions in this system are very sensitive to Cu vacancies and Cu/Mn site mixing.
We report the discovery of a field driven transition from a striped to woven Spin Density Wave (SDW) in the tetragonal heavy fermion compound CeAuSb$_2$. Polarized along $bf c$, the sinusoidal SDW amplitude is 1.8(2) $mu_B$/Ce for $T ll T_N$=6.25(10) K with wavevector ${bf q}_{1}=( eta, eta, frac{1}{2} )$ ($eta=0.136(2)$). For ${bf H}parallel{bf c}$, harmonics appearing at $2{bf q}_{1}$ evidence a striped magnetic texture below $mu_circ H_{c1}=2.78(1)$ T. Above $H_{c1}$, these are replaced by woven harmonics at ${bf q}_{1}+{bf q}_2=(2eta, 0, 0)+{bf c}^*$ until $mu_circ H_{c2}=5.42(5)$ T, where satellites vanish and magnetization non-linearly approaches saturation at 1.64(2) $mu_B$/Ce for $mu_circ Happrox 7$ T.
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