We present magnetic and transport properties of PrRh$_{2}$Si$_{2}$ single crystals which exhibit antiferromagnetic order below T$_{N}$ = 68 K. Well defined anomalies due to magnetic phase transition are observed in magnetic susceptibility, resistivity, and specific heat data. The T$_{N}$ of 68 K for PrRh$_{2}$Si$_{2}$ is much higher than 5.4 K expected on the basis of de-Gennes scaling. The magnetic susceptibility data reveal strong uniaxial anisotropy in this compound similar to that of PrCo$_{2}$Si$_{2}$. With increasing pressure T$_{N}$ increases monotonically up to T$_N$ = 71.5 K at 22.5 kbar.
We have explored the possibility to orient spins in antiferromagnetic thin films with low magnetocrystalline anisotropy via the exchange coupling to adjacent antiferromagnetic films with high magnetocrystalline anisotropy. We have used MnO as a prototype for a system with negligible single-ion anisotropy. We were able to control its spin direction very effectively by growing it as a film on antiferromagnetic CoO films with different predetermined spin orientations. This result may pave the way for tailoring antiferromagnets with low magnetocrystalline anistropy for applications in exchange bia…
We report measurements on single crystals of orthorhombic CeNiGe2, which is found to exhibit highly anisotropic magnetic and transport properties. The magnetization ratio M(H//b)/M(H^b) at 2 K is observed to be about 18 at 4 T and the electrical resistivity ratio r//b/r^b is about 70 at room temperature. It is confirmed that CeNiGe2 undergoes two-step antiferromagnetic transition at 4 and 3 K, as reported for polycrystalline samples. The application of magnetic field along the b axis (the easy magnetization axis) stabilizes a ferromagnetic correlation between the Ce ions and enhances the hoppi…
From a systematic study of the electrical resistivity $ρ(T,H)$, magnetic susceptibility $χ(T,H)$, isothermal magnetization $M(H)$ and the specific heat $C(T,H)$, a temperature-magnetic field ($T$-$H$) phase diagram has been established for GdCo$_{1-x}$Fe$_x$AsO ($x = 0$ and $0.05$) polycrystalline compounds. GdCoAsO undergoes two long-range magnetic transitions: ferromagnetic (FM) transition of Co $3d$ electrons ($T_\textup{C}^\textup{Co}$) and antiferromagnetic (AFM) transition of Gd $4f$ electrons ($T_\textup{N}^\textup{Gd}$). For the Fe-doped sample ($x=0.05$), an extra magnetic reorientati…
Giant Magnetocrystalline Anisotropy in Honeycomb Iridate NiIrO3 with Large Coercive Field Exceeding 17 T
School of Chemistry, Sun Yat-Sen University（中山大学化学学院）；School of Chemistry and Environment, Jiaying University（嘉应学院化学与环境学院）；School of Physics, Sun Yat-Sen University（中山大学物理学院）；School of Physics, Huazhong University of Science and Technology（华中科技大学物理学院）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；School of Chemistry and Chemical Engineering, Hainan University（海南大学化学化工学院）
Structural and thermodynamic properties of single-crystalline UNi$_{1-x}$Ge$_2$ with $x$\,=\,0.66 have been investigated by measuring magnetization, specific heat, and thermal expansion over a wide range of temperatures and magnetic fields. The measurements revealed the emergence of a long-range antiferromagnetic ordering of uranium magnetic moments below the N{é}el temperature $T_{\rm N}$\,=\,45.5\,K and the existence of two easy axes in the studied compound, namely $b$ and $c$, which correspond to the planes of the uranium zig-zag chains. Magnetic field applied along these two crystallograph…
We report on the single crystal growth and anisotropic physical properties of CeAgAs$_2$. The compound crystallizes as on ordered variant of the HfCuSi$_2$-type crystal structure and adopts the orthorhombic space group $Pmca$~(\#57) with two symmetry inequivalent cerium atomic positions in the unit cell. The orthorhombic crystal structure of our single crystal was confirmed from the powder x-ray diffraction and from electron diffraction patterns obtained from the transmission electron microscope. The anisotropic physical properties have been investigated on a good quality single crystal by mea…
Antiferromagnetic spintronics actively introduces new principles of magnetic memory, in which the most fundamental spin-dependent phenomena, i.e. anisotropic magnetoresistance effects, are governed by an antiferromagnet instead of a ferromagnet. A general scenario of the antiferromagnetic anisotropic magnetoresistance effects mainly stems from the magnetocrystalline anisotropy related to spin-orbit coupling. Here we demonstrate magnetic field driven contour rotation of the fourfold anisotropic magnetoresistance in bare antiferromagnetic Sr2IrO4/SrTiO3 (001) thin films hosting a strong spin-orb…
The magnetic structure of antiferromagnetic NdRhIn5 has been determined using neutron diffraction. It has a commensurate antiferromagnetic structure with a magnetic wave vector (1/2,0,1/2) below T_N = 11K. The staggered Nd moment at 1.6K is 2.6mu_B aligned along the c-axis. We find the magnetic structure to be closely related to that of its cubic parent compound NdIn3 below 4.6K. The enhanced T_N and the absence of additional transitions below T_N for NdRhIn5 are interpreted in terms of an improved matching of the crystalline-electric-field (CEF), magnetocrystalline, and exchange interaction a…
Anisotropic magnetic properties of single crystalline RAu_{2}Ge_{2} (R = La, Ce and Pr) compounds are reported. LaAu_{2}Ge_{2} exhibit a Pauli-paramagnetic behavior whereas CeAu_{2}Ge_{2} and PrAu_{2}Ge_{2} show an antiferromagnetic ordering with N\grave{e}el temperatures T_{N} = 13.5 and 9 K, respectively. The anisotropic magnetic response of Ce and Pr compounds establishes [001] as the easy axis of magnetization and a sharp spin-flip type metamagnetic transition is observed in the magnetic isotherms. The resistance and magnetoresistance behavior of these compounds, in particular LaAu_{2}Ge_{…
The square Bi layers in $A$MnBi$_2$ ($A =$ Sr, Ca) host Dirac fermions which coexist with antiferromagnetic order on the Mn sublattice below $T_\mathrm{N} = 290\,$K (Sr) and $270\,$K (Ca). We have measured the spin-wave dispersion in these materials by triple-axis neutron spectroscopy. The spectra show pronounced spin gaps of 10.2(2)$\,$meV (Sr) and 8.3(8)$\,$meV (Ca) and extend to a maximum energy transfer of 61 - 63$\,$meV. The observed spectra can be accurately reproduced by linear spin-wave theory from an Heisenberg effective spin Hamiltonian. Detailed global fits of the full magnon disper…
We report on the magnetocrystalline anisotropy energy (MAE) and spin reorientation in antiferromagnetic state of spin $S=1/2$ tetramer system SeCuO$_3$ observed in torque magnetometry measurements in magnetic fields $H<5$~T and simulated using density functional calculations. We employ simple phenomenological model of spin reorientation in finite magnetic field to describe our experimental torque data. Our results strongly support collinear model for magnetic structure in zero field with possibility of only very weak canting. Torque measurements also indicate that, contrary to what is expected…
Magnetization and specific heat measurements on a UIrSi3 single crystal reveal Ising-like antiferromagnetism below T$_N$ = 41.7 K with easy magnetization direction along the c-axis of tetragonal structure. The antiferromagentic ordering is suppressed by magnetic fields > H$_c$ (μ$_0$H$_c$ = 7.3 T at 2 K) applied along the c-axis. The first-order metamagnetic transition at H$_c$ exhibits asymmetric hysteresis reflecting a slow reentry of the complex ground-state antiferromagnetic structure with decreasing field. The hysteresis narrows with increasing temperature and vanishes at 28 K. A second-o…
The magnetocrystalline anisotropy exhibited in PrPd$_2$Ge$_2$ single crystal has been investigated by measuring the magnetization, magnetic susceptibility, electrical resistivity and heat capacity. PrPd$_2$Ge$_2$ crystallizes in the well known ThCr$_2$Si$_2$\--type tetragonal structure. The antiferromagnetic ordering is confirmed as 5.1~K with the [001]-axis as the easy axis of magnetization. A superzone gap formation is observed from the electrical resistivity measurement when the current is passed along the [001] direction. The crystal electric field (CEF) analysis on the magnetic susceptibi…
The scenario of a metal-insulator transition driven by the onset of antiferromagnetic order in NaOsO$_3$ calls for a trustworthy derivation of the underlying effective spin Hamiltonian. To determine the latter we rely on {\it ab initio} electronic-structure calculations, linear spin-wave theory, and comparison to experimental data of the corresponding magnon spectrum. We arrive this way to Heisenberg couplings that are $\lesssim$45\% to$\lesssim$63\% smaller than values presently proposed in the literature and Dzyaloshinskii-Moriya interactions in the region of 15\% of the Heisenberg exchange …
We report on the synthesis of a new $γ$-phase of the spin $S$~=~$\frac{3}{2}$ compound SrCo$_2$(PO$_4$)$_2$ together with a detailed structural, magnetic and thermodynamic properties. The $γ$-phase of SrCo$_2$(PO$_4$)$_2$ crystallizes in a triclinic crystal structure with the space group $P\bar{1}$. Susceptibility and specific heat measurements reveal that SrCo$_2$(PO$_4$)$_2$ orders antiferromagnetically below $T_{\rm N}\simeq 8.5$\,K and the nature of ordering is three dimensional (3D). The magnetic isotherm at temperatures below $T_{\rm N}$ shows a field-induced spin-flop transition, relate…
The different magnetic phases of the intermetallic compound Nd$_5$Ge$_3$ are studied in terms of the specific heat, in a broad range of temperatures (350~mK--140~K) and magnetic fields (up to 40 kOe). The expected $T^{3}$ and $T^{3/2}$ terms are not found in the antiferromagnetic (AFM) and ferromagnetic (FM) phases respectively, but a gapped $T^2$ contribution that originates from a mixture of AFM and FM interactions in different dimensionalities under a large magnetocrystalline anisotropy, is present in both. An almost identical Schottky anomaly, that arises from the hyperfine splitting of th…
We grew high-quality single crystals of the 5f electron van der Waals compound UI$_3$ and investigated them by measurements of specific heat and magnetization as functions of temperature and magnetic field. UI$_3$ behaves as an antiferromagnet with a first-order magnetic phase transition at the Neél temperature $T_N$ = 2.65 K. It is characterized by a sharp symmetric specific-heat peak which is gradually shifted to lower temperatures by increasing magnetic field applied along either the a- or b-axis. The behavior in magnetic fields reveals orthorhombic magnetocrystalline anisotropy with the ha…
Iridates supply fertile grounds for unconventional phenomena and exotic electronic phases. With respect to well-studied octahedrally-coordinated iridates, we pay our attention to a rather unexplored iridate, Na4IrO4, showing an unusual square-planar coordination. The latter is key to rationalize the electronic structure and magnetic property of Na4IrO4, which is here explored by first-principles density functional theory and Monte Carlo simulations. Due to the uncommon square-planar crystal field, Ir 5d states adopt intermediate-spin state with double occupation of dz2 orbital, leading to a si…
Single crystals of R$_2$CoGa$_8$ series of compounds were grown, for the first time, by high temperature solution growth (flux) method. These compounds crystallize in a tetragonal crystal structure with the space group $P4/mmm$. It has been found that R$_2$CoGa$_8$ phase forms only with the heavier rare earths, starting from Gd with a relatively large $c/a$ ratio of $\approx$ 2.6. The resultant anisotropic magnetic properties of the compounds were investigated along the two principal crystallographic directions of the crystal viz., along [100] and [001]. The nonmagnetic compounds Y$_2$CoGa$_8$…
CeCd$_3$P$_3$ and CeCd$_3$As$_3$ compounds adopt the hexagonal ScAl$_3$C$_3$-type structure, where magnetic Ce ions on a triangular lattice order antiferromagnetically below $T_\text{N} \sim$0.42~K. Their crystalline electric field (CEF) level scheme has been determined by fitting magnetic susceptibility curves, magnetization isotherms, and Schottky anomalies in specific heat. The calculated results, incorporating the CEF excitation, Zeeman splitting, and molecular field, are in good agreement with the experimental data. The CEF model, with Ce$^{3+}$ ions in a trigonal symmetry, explains the s…
The 3$d$-5$d$ based double perovskites offer an ideal playground to study the interplay between electron correlation ($U$) and spin-orbit coupling (SOC) effect, showing exotic physics. The Sr$_2$FeIrO$_6$ is an interesting member in this family with ionic distribution of Fe$^{3+}$ (3$d^5$) and Ir$^{5+}$ (5$d^4$) where the later is believed to be nonmagnetic under the picture of strong SOC. Here, we report detailed investigation of structural, magnetic and electronic transport properties along with electronic structure calculations in (Sr$_{1-x}$Ca$_x$)$_2$FeIrO$_6$ series with $x$ from 0 to 1.…
Antisite-disorder driven tuning of magnetic properties and exchange-bias in Nd$_{2-x}$Sr$_{x}$CoMnO$_{6-δ}$ $(0 \leq x \leq 1)$ ($δ\sim 0.5$) double perovskites
Indian Institute of Technology Kharagpur（印度理工学院卡拉格普尔分校）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；TU Delft Reactor Institute（代尔夫特理工大学反应堆研究所）
