Magnetic diffraction of polarized neutrons by the cubic Laves compound UAl2 in a magnetic field has unveiled weak Bragg spots that are nominally forbidden. On the one hand, they can be viewed as magnetic analogues of the basis-forbidden (2, 2, 2) reflection in diamond-type structures that has been painstakingly and frequently investigated over almost a century. Alternatively, the pattern of weak intensities can be assigned to Dirac multipoles imbedded in field-induced magnetic charge. To this end, a published diffraction pattern is successfully confronted with intensities calculated from the appropriate magnetic space-group that includes Dirac dipoles (anapoles) to describe the basis-forbidden magnetic reflections, and conventional (axial) dipole and octupole multipoles to describe basis-allowed magnetic reflections.
The magnetic properties and magnetocaloric effect of an intermetallic compound $\mathrm{Er_2Rh_3Si}$ was investigated by performing temperature dependence of dc- and ac-magnetic susceptibility and isothermal magnetizations. Polycrystalline $\mathrm{Er_2Rh_3Si}$ compound with $\mathrm{Mg_2Ni_3Si}$-type of rhombohedral Laves phases (space group $R\overline{3}m$, hR18) structure was synthesized by arc-melting method. The ac- and dc-magnetic susceptibility results revealed that the compound exhibited ferromagnetic order with $T_C$ $\approx$ 18 K. The obtained isothermal magnetic entropy changes ($…
A C14 Nb0.975Fe2.025 Laves phase compound was investigated aimed at determining the H-T magnetic phase diagram. Magnetization, M, and AC magnetic susceptibility measurements were performed. Concerning the former field-cooled and zero-field-cooled M-curves were recorded in the temperature range of 2-200K and in applied magnetic field, H, up to 1000 Oe, isothermal M(H) curves at 2 K, 5 K, 50 K, 80 K and 110 K as well as hysteresis loops at several temperatures over the field range of -10 to +10kOe. Regarding the AC susceptibility, both real and imaginary components were registered as a function …
C14 Nb(Fe89.4Al10.6)2 Laves phase intermetallic compound was investigated by DC magnetization (M) measurements performed in the temperature (T) interval of 20 to 175 K,under an applied magnetic field (H) ranging between 50 and 1250 Oe. Magnetization curves were recorded in the field-cooled (FC) and in the zero-field-cooled (ZFC) modes. They clearly showed an irreversible character that vanished at H=1250 Oe. Both magnetization curves exhibited well-defined peaks around T_N =72.3 K whose positions were H-independent, so they were identified as the compound's Néel temperature. The existence of i…
C14 Laves phase Nb0.975Fe2.025 compound was investigated by means of the Mössbauer spectroscopy. Spectra were recorded in the temperature range of 5-300K. Their analysis in terms of three sub spectra yielded information on magnetic and lattice dynamical properties of Fe atoms regularly occupying 2a and 6h lattice sites and, excessively, 4f sites. No indication of magnetism was observed down to the temperature of T=ca.50K, and spectral parameters viz. center shift, CS, and the main component of the electric field gradient, Vzz, behave regularly. In particular, analysis of CS(T) in terms of the …
We report experimentally observed linear dichroism in angle-resolved core-level photoemission spectra of PrIr2Zn20 and PrB6 in cubic symmetry. The different anisotropic 4f charge distributions between the compounds due to the crystalline-electric-field splitting are responsible for the difference in the linear dichroism, which has been verified by spectral simulations with the full multiplet theory for a single-site Pr3+ ion in cubic symmetry. The observed linear dichroism and polarization-dependent spectra in two different photoelectron directions for PrIr2Zn20 are reproduced by theoretical a…
The Crystalline Electric Field (CEF) influence is usually described by considering an ideally symmetrical rare-earth site. In the case of cage compounds, ample excursions of the rare-earth inside the cage require an adapted CEF description. A corrective, position dependent, CEF term accounts for the deviation from the perfect symmetry. In the paramagnetic range, a CEF level with orbital degeneracy thus acquires a width reflecting the rare-earth spatial distribution. In the case, frequent in cubic systems, of an orbitally degenerate CEF ground state at the center, this width introduces an addit…
We theoretically study the stability of magnetic skyrmion crystals (SkXs) in chiral cubic antiferromagnets with the EuPtSi hosting unconventional nanometric SkXs in mind. By performing numerical simulations for a minimal effective spin model with the long-range Dzyaloshinskii-Moriya interaction and the multiple-spin interaction arising from itinerant nature of electrons, we clarify two key ingredients for the emergence of the SkXs in EuPtSi: One is the low-symmetric ordering vectors that lead to the field-direction sensitive SkXs in an external magnetic field, while the other is the synergy be…
The role of ionic sizes in inducing the cubic to tetragonal distortion in AV$_{2}$O$_{4}$ and ACr$_{2}$O$_{4}$ (A=Zn, Mg and Cd) compounds
尖晶石型化合物中立方相到四立方相的畸变在过去二十年一直是一个有争议的问题。不同的研究小组提出了不同的机制来理解这些尖晶石中的这种畸变，它们是：（i）称为自旋驱动Jahn-Teller（JT）效应的自旋晶格耦合机制，（ii）强相对论自旋轨道耦合，适度JT畸变和弱V-V相互作用以及（iii）JT效应。现在，为了知道这种扭曲的可能原因，我们通过进行自旋非极化计算来避免这些复杂性（自旋、电子、轨道和晶格自由度之间的各种相互作用）。ZnV $_{2}$ O $_{4}$（ZnCr $_{2}$ O $_{4}$）、MgV $_{2}$ O $_{4}$（MgCr $_{2}$ O $_{4}$）和CdV $_{2}$ O $_{4}$（CdCr $_{2}$ O $_{4}$）的体积模量的计算值分别为$\sim$ 289（$\sim$ 254）、$\sim$ 244（$\sim$ 243）和$\sim$ 230（$\sim$ 233）GPa。对于钒酸盐和铬酸盐，晶格参数$a$的计算值顺序分别为$_{2}$和$_{2}$，与实验结果一致.三次到四次畸变（c/a）的计算值，对于ZnV $_{2}$ O $_{4}$，c/a $<$ 1（ZnCr $_{2}$ O $_{4}$）、MgV $_{2}$ O $_{4}$（MgCr $_{2}$ O $_{4}$）和CdV $_{2}$ O $_{4…
The structural, electronic, and magnetic properties of bulk GdCu (CsCl-type) are investigated using spin density functional theory, where highly localized $4f$ orbitals are treated within LDA+$U$ and GGA+$U$ methods. The calculated magnetic ground state of GdCu using collinear as well as spin spiral calculations exhibits a C-type antiferromagnetic configuration representing a spin spiral propagation vector $\mathbf{Q}=\frac{2π}{a}(\frac{1}{2},\frac{1}{2},0)$. The parameters of the effective Heisenberg Hamiltonian are evaluated from a self-consistent electronic structure and are used to determi…
A first order phase transition induced by magnetic field and temperature
以赝二元C15-Laves相化合物Ce（Fe $_{0.96}$ Al $_{0.04}$）$_2$作为研究铁磁（FM）到反铁磁（AFM）相变的范例，我们提出了在此FM-AFM转变的磁输运测量中有趣的热磁历史效应.我们认为，这些独特的滞后功能可以用来识别的确切性质-一阶或二阶-这种过渡的磁系统中的电输运是强烈相关的基本磁秩序。与在具有钙钛矿型结构的Nd和Pr基锰化合物中观察到的类似FM-AFM转变进行了比较。
We report complex magnetic, magnetoresistance (MR) and magnetocaloric properties of Gd4RhAl and Tb4RhAl forming in the Gd4RhIn type cubic structure. Though the synthesis of the compounds was reported long ago, to our knowledge, no attempt was made to investigate the properties of these compounds. The present results of ac and dc magnetization, electrical resistivity and heat-capacity measurements down to 1.8 K establish that these compounds undergo antiferromagnetic order initially, followed by complex spin-glass features with decreasing temperature. These characteristic temperatures are: For …
We consider possible high temperature superconductivity (high-T$_c$) in transition metal compounds with a cubic zinc-blende lattice structure. When the electron filling configuration in the d-shell is close to d$^7$, all three t$_{2g}$ orbitals are near half filling with strong nearest neighbor antiferromagnetic (AFM) superexchange interactions. We argue that upon doping, this electronic environment can be one of "genes" to host unconventional high T$_c$ with a time reversal symmetry broken $d_{2z^2-x^2-y^2} \pm i d_{x^2-y^2}$ pairing symmetry. With gappless nodal points along the diagonal dir…
The beryllides MBe13 (M = rare earths and actinides) crystallize in a NaZn13-type cubic structure, which can be categorized as a cage-structured compound. In this study, powder X-ray diffraction measurements have been performed on LaBe13, SmBe13, and UBe13 in the temperature range between 7 and 300 K in order to investigate their crystallographic characteristics systematically. They keep the NaZn13-type cubic structure down to the lowest temperature. We estimated their Debye temperature to be 600 - 750 K from analyses of the temperature dependence of a lattice parameter, being in good agreemen…
The New High-entropy Compound RhMnFeCoGe4 with Cubic Non-centrosymmetric B20 Structure
Vereshchagin Institute for High Pressure Physics, RAS（俄罗斯科学院维列夏金高压物理研究所）；Mikheev Institute of Metal Physics, Russian Academy of Sciences（俄罗斯科学院米凯耶夫金属物理研究所）
Cubic Pr-based compounds with $Γ_3$ non-Kramers doublet ground states can realize a novel heavy Fermi liquid with spinorial hybridization ('hastatic' order) that breaks time reversal symmetry. Several Pr-"1-2-20" materials exhibit a suggestive heavy Fermi liquid stabilized in intermediate magnetic fields; these provide key insight into the quadrupolar Kondo lattice. We develop a simple, yet realistic microscopic model of ferrohastatic order, and elaborate its experimental signatures and behavior in field, where it is a good candidate to explain the observed heavy Fermi liquids at intermediate …
We present a study on the magnetic susceptibility $χ(T)$ and electrical resistance, as a function of temperature and magnetic field $R(T,H)$, of the ferromagnetic heavy fermion YbNi$_2$. The X-ray diffraction analysis shows that the synthesized polycrystalline samples crystallizes in the cubic Laves phase structure C15, with a spatial group $Fd\overline{3}m$. The magnetic measurements indicate a ferromagnetic behavior with transition temperature at 9 K. The electrical resistance is metallic-like at high temperatures and no signature of Kondo effect was observed. In the ferromagnetic state, the…
The magnetic ground states of $R_2$Ru$_2$O$_7$ and $A_2$Ru$_2$O$_7$ with $R=$ Pr, Gd, Ho, and Er, as well as $A=$ Ca, Cd are predicted devising a combination of the cluster-multipole (CMP) theory and spin-density-functional theory (SDFT). The strong electronic correlation effects are estimated by the constrained-random-phase approximation (cRPA) and taken into account within the dynamical-mean-field theory (DMFT). The target compounds feature $d$-orbital magnetism on Ru$^{4+}$ and Ru$^{5+}$ ions for $R$ and $A$, respectively, as well as $f$-orbital magnetism on the $R$ site, which leads to an …
Within the framework of the $s$-$d(f)$ exchange model in the mean-field approximation for square, simple cubic, body-centered and face-centered cubic lattices, the formation of a ferromagnetic, spiral, and commensurate antiferromagnetic order is investigated. The possibility of the formation of inhomogeneous states (magnetic phase separation), which necessarily arises during first-order phase transitions in the electron filling parameter, is taken into account. The saturation of the antiferromagnetic and spiral states is studied depending on the parameters of the model. The results obtained in…
Direct determination of the crystal field parameters of Dy, Er and Yb impurities in the skutterudite compound CeFe$_{4}$P$_{12}$ by Electron Spin Resonance
尽管在过去的十年里对方钴矿进行了广泛的研究，但它们的电晶体场基态仍然是一个有争议的问题。我们表明，电子自旋共振（ESR）测量可以确定完整的晶场参数（CFPs）的Th立方对称性（Im 3）的Ce $_{1-x}$ R $_{x}$ Fe $_{4}$ P $_{12}$（R = Dy，Er，Yb，$x\lesssim 0.003$）方钴矿化合物。根据ESR数据的分析，确定了Ce $^{3+}$位点上这些稀土中的每一种的三个CFPs，B4c，B6c和B6t。场和温度依赖性的掺杂晶体的测量磁化强度是在一个很好的协议与来自ESR的CFPs Bnm预测。
Magnetic susceptibility, specific heat, and electrical resistivity measurements have been performed on single-crystal EuBe13 in the temperature range between 2 and 300 K to investigate its phonon property and the valence state of the Eu ion. The obtained temperature dependence of the magnetic susceptibility curves obey a typical Van Vleck susceptibility for Eu3+ with a nonmagnetic ground state in the entire measured temperature range. In the case of the specific heat, we observed the coexistence of Debye and Einstein phonon modes with characteristic Debye and Einstein temperatures of ~ 835 K a…
Crystal structure, electronic state of Ir$^{4+}$, and magnetic properties of the antifluorite compound K$_2$IrBr$_6$ are studied using high-resolution synchrotron x-ray diffraction, resonant inelastic x-ray scattering (RIXS), thermodynamic and transport measurements, and ab initio calculations. The crystal symmetry is reduced from cubic at room temperature to tetragonal below 170 K and eventually to monoclinic below 122 K. These changes are tracked by the evolution of the non-cubic crystal-field splitting $Δ$ measured by RIXS. Non-monotonic changes in $Δ$ are ascribed to the competing effects …
