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We report synthesis of single crystalline NaMnAs, confirm its antiferromagnetic order and characterise the sample by photoemission spectroscopy. The electronic structure was studied using optical transmittance, x-ray and ultraviolet spectroscopy and by theoretical modeling using local density approximation (LDA) extended to LDA+U when Heisenberg model parameters were determined. Optical transmittance measurement have confirmed the theoretical predictions that NaMnAs is a semiconductor. Also the N\'eel temperature was closer determined for the first time from temperature dependence of magnetization, in agreement with our Monte Carlo simulations., Comment: 11 pages, 11 figures

The effect of Cu substitution on the stability of the CuMnAs tetragonal phase was studied both experimentally and by ab initio calculations. Polycrystalline samples with various compositions Cu$_{1+x}$Mn$_{1-x}$As $(x = 0 - 0.5)$ were synthetized. The tetragonal phase of CuMnAs is found to be stabilized by substituting Mn by Cu in the amount of $x$ ~ 0.1 or higher. This observation is supported by ab initio calculations of the total energy of the tetragonal and orthorhombic phases; with increasing Cu content the tetragonal phase is favoured. Small variations of composition thus allow to grow selectively one of these two phases with distinct and unique features for antiferromagnetic spintronics. Measurements of magnetic susceptibility and differential scanning calorimetry have shown that the tetragonal Cu$_{1+x}$Mn$_{1-x}$As has an antiferromagnetic behaviour with the maximum N\'eel temperature $T_N$ = 507 K for the highest Mn content samples, decreasing with the decreasing Mn content.

We report on an infrared magneto-spectroscopy study of Pb$_{1-x}$Sn$_x$Se, a topological crystalline insulator. We have examined a set of samples, all in the inverted regime of electronic bands, with the tin composition varying from $x=0.2$ to $0.33$. Our analysis shows that the observed response, composed of a series of interband inter-Landau level excitations, can be interpreted and modelled using the relativistic-like Hamiltonian for three-dimensional massive Dirac electrons, expanded to include diagonal quadratic terms that impose band inversion. In our data, we have not found any clear signature of massless electron states that are present on the surface of Pb$_{1-x}$Sn$_x$Se crystals in the inverted regime. Reasons for this unexpected result are discussed., 11 pages, 7 figures, to be published in Phys. Rev. B

Evolution of magnetism in single crystals of the van der Waals compound $\mathrm{V}{\mathrm{I}}_{3}$ in external pressure up to 7.3 GPa studied by measuring magnetization and ac magnetic susceptibility is reported. Four magnetic phase transitions, at ${T}_{1}=54.5\phantom{\rule{0.16em}{0ex}}\mathrm{K}, {T}_{2}=53\phantom{\rule{0.16em}{0ex}}\mathrm{K}, {T}_{\mathrm{C}}=49.5\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and ${T}_{\mathrm{FM}}=26\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, respectively, have been observed at ambient pressure. The first two have been attributed to the onset of ferromagnetism in specific crystal-surface layers. The bulk ferromagnetism is characterized by the magnetic ordering transition at Curie temperature ${T}_{\mathrm{C}}$ and the transition between two different ferromagnetic phases ${T}_{\mathrm{FM}}$, accompanied by a structure transition from monoclinic to triclinic symmetry upon cooling. The pressure effects on magnetic parameters were studied with three independent techniques. ${T}_{\mathrm{C}}$ was found to be almost unaffected by pressures up to 0.6 GPa whereas ${T}_{\mathrm{FM}}$ increases rapidly with increasing pressure and reaches ${T}_{\mathrm{C}}$ at a triple point at \ensuremath{\approx} 0.85 GPa. At higher pressures, only one magnetic phase transition is observed moving to higher temperatures with increasing pressure to reach 99 K at 7.3 GPa. In contrast, the low-temperature bulk magnetization is significantly reduced by applying pressure (by more than 50% at 2.5 GPa) suggesting a possible pressure-induced reduction of vanadium magnetic moment. First-principles calculations of $\mathrm{V}{\mathrm{I}}_{3}$ under pressure allow us to ascribe the evolution of ${T}_{\mathrm{C}}$ with pressure to the reduction of interplanar distance, including the observed slope change at 0.6 GPa. These calculations also describe the associated band gap closing, showing that with a modest compression the material would become metallic. Overall, the large pressure range covered corresponds to a significant change of interplanar interactions. The obtained data thus allow us to shed light on how does the transition between the three-dimensional (3D) and quasi-2D system affect magnetic interactions in the system.

We present acoustic signatures of the electric quadrupolar degrees of freedom in the honeycomb-layer compound UNi$_4$B. The transverse ultrasonic mode $C_{66}$ shows softening below 30 K both in the paramagnetic phase and antiferromagnetic phases down to $\sim0.33$ K. Furthermore, we traced magnetic field-temperature phase diagrams up to 30 T and observed a highly anisotropic elastic response within the honeycomb layer. These observations strongly suggest that $\Gamma_6$(E$_{\rm 2g}$) electric quadrupolar degrees of freedom in localized $5f^2$ ($J = 4$) states are playing an important role in the magnetic toroidal dipole order and magnetic-field-induced phases of UNi$_4$B, and evidence some of the U ions remain in the paramagnetic state even if the system undergoes magnetic toroidal ordering., Comment: 6 pages, 4 figures + Supplemental Materials (11 pages, 9 figures)

Temperature-dependent resistivity and magnetoresistance are measured in bulk tetragonal phase of antiferromagnetic CuMnAs and the latter is found to be anisotropic both due to structure and magnetic order. We compare these findings to model calculations with chemical disorder and finite-temperature phenomena included. The finite-temperature ab initio calculations are based on the alloy analogy model implemented within the coherent potential approximation and the results are in fair agreement with experimental data. Regarding the anisotropic magnetoresistance (AMR) which reaches a modest magnitude of 0.12%, we phenomenologically employ the Stoner-Wohlfarth model to identify temperature-dependent magnetic anisotropy of our samples and conclude that the field-dependence of AMR is more similar to that of antiferromagnets than ferromagnets, suggesting that the origin of AMR is not related to isolated Mn magnetic moments., 10+ pages, few minor issues corrected

Our present study on oriented single crystal revealed huge magneto-crystalline anisotropy with respect to principal crystallographic axes, even several magnetic transitions were observed below TN = 748 K (c-axis) at 700 K (a-axis) as well 657 K (b-axis). The spin reorientation of magnetic moment takes place in very narrow temperature range between 135 K and 125 K and is attributed to vanishing of ferromagnetic component aligned along b-axis. Measurements of magnetic isotherms trace the development of ferromagnetic component and revealed the intermediate temperature range between 120 K and 20 K which is characterised by zero ferromagnetic components in any principal crystal direction. The ferromagnetic component develops consecutive at low temperature below 20 K along a-axis. Our study indicates completely different magnetic structure of NdFe0.9Mn0.1O3 below 135 K in comparison with NdFeO3.

Permalloy is a widespread material used in numerous fundamental experiments and novel spintronic, optoelectronic devices. In order to model their response or tailor the optimal experimental parameters it is necessary to know the optical and magneto-optical properties of this material over a wide spectral range. We report on the systematic study of optical and magneto-optical properties of 10 nm and 150 nm thick permalloy films by means of spectroscopic ellipsometry and magneto-optical spectroscopy. To study the influence of the surface oxidization, the samples were prepared with and without Au capping layer. Spectral dependence of the complete permittivity tensor was derived from experimental data in a broad spectral range covering IR, visible and UV regions. All samples exhibited metallic-like optical and magneto-optical properties with clear differences in 10 nm thick bare sample. These differences to overall optical and magneto-optical properties of nanometer-thick permalloy layers were ascribed to a strong influence of the surface oxide. Keywords: Permalloy, Thin films, Spectroscopic ellipsometry, Magnetooptical Kerr effect spectroscopy, Complex permittivity tensor, Oxidation

We performed 27Al-NMR measurements for the CaBe2Ge2 type single crystalline LaPd2Al2 in the temperature range from 100 K to 5 K to investigate the origin of the structural phase transition. We found that the line profile of the 27Al-NMR spectrum does not change entirely on passing through the structural phase transition at T st . Meanwhile, the peak position of the central line slightly change ( ≈ 30 ppm) below 70 K, suggesting the orbital shift changes below T st . The present 27Al-NMR studies evidence that the local electronic state at Al site is hardly affected by the structural phase transition.

Single crystals of ThBe13 and LuBe13 have been prepared using aluminum flux method. The crystals structure of both compounds was confirmed to be cubic of the NaZn13-type with the lattice parameters a = 10.183(6) A and a = 10.395(3) A for LuBe13 and ThBe13, respectively. The low temperature measurements of electrical resistance and ac susceptibility have revealed a BCS-type of superconductivity in ThBe13 below Tc = 125 mK. LuBe13 has been found to be superconducting below Tc = 630 mK.

Two conflicting ground states, i.e., an antiferromagnetic ground state at 3.8 K and a ferromagnetic ground state at 5.1 K, have been reported for $\mathrm{CePtG}{\mathrm{e}}_{2}$, which has two nonequivalent crystallographic Ce sites. In this study, we have prepared polycrystalline and single-crystalline $\mathrm{CePtG}{\mathrm{e}}_{2}$ samples and measured their magnetization, specific heat, resistivity, and Seebeck coefficient. The observed bend in resistivity, peak in magnetic susceptibility, and \ensuremath{\lambda}-type anomaly in specific heat at ${T}_{N}=3.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and the metamagnetic transition in this $\mathrm{CePtG}{\mathrm{e}}_{2}$ suggest antiferromagnetism at low temperatures. No evidence of ferromagnetic order was found in the studied temperature range, indicating possible crystal polymorphism with ferromagnetic character. The large susceptibility around ${T}_{N}$ and the Schottky-type specific heat indicate a well-localized $f$-electron state. However, the large residual \ensuremath{\gamma} and \ensuremath{\chi}(0) indicate an itinerant heavy $f$-electron state. These findings suggest the coexistence of localized and heavy itinerant states corresponding to $f$ electrons at the two Ce sites in this antiferromagnetic $\mathrm{CePtG}{\mathrm{e}}_{2}$. The field dependence of magnetization indicates a sudden increase in magnetization at weak magnetic fields $(\ensuremath{\sim}0.2\phantom{\rule{0.16em}{0ex}}\mathrm{T})$, followed by a plateau at fields above 0.2 T, resulting in a possible different polarized metamagnetic state via interaction between localized and itinerant $f$ electrons.

Surface magnetic domains of a UCoGa single crystal during magnetization/demagnetization processes in increasing/decreasing magnetic fields were investigated by means of magnetic-force-microscopy (MFM) images at low temperatures. The observed domain structure is typical for a ferromagnet with strong uniaxial anisotropy. The evolution of magnetic domains during cooling of the crystal below TC has also been manifested by MFM images. Analysis of the available data reveals that the high uniaxial magnetocrystalline energy in combination with the relatively small ferromagnetic exchange interaction in UCoGa gives rise to the formation of very narrow domain walls formed by the pairs of the nearest U neighbor ions with antiparallel magnetic moments within the basal plane. Since the very high anisotropy energy is a common feature of the majority of the uniaxial U ferromagnets, analogous domain-wall properties are expected for all these materials.

Thermal expansion, magnetostriction, and magnetization measurements under magnetic field and hydrostatic pressure were performed on a ${\mathrm{UAu}}_{2}{\mathrm{Si}}_{2}$ single crystal. They revealed a large anisotropy of magnetoelastic properties manifested by prominent length changes, leading to a collapse of the unit-cell volume accompanied by breaking the fourfold symmetry (similar to that in ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$ in the hidden-order state) in the antiferromagnetic state as consequences of strong magnetoelastic coupling. The magnetostriction curves measured at higher temperatures confirm a bulk character of the $50\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ weak ferromagnetic phase. The large positive pressure change of the ordering temperature predicted from Ehrenfest relation contradicts the more than an order of magnitude smaller pressure dependence observed by the magnetization and specific heat measured under hydrostatic pressure. A comprehensive magnetic phase diagram of ${\mathrm{UAu}}_{2}{\mathrm{Si}}_{2}$ in magnetic field applied along the $c$ axis is presented. The ground-state antiferromagnetic phase is suppressed by a field-induced metamagnetic transition that changes its character from second to first order at the tricritical point.

Tetragonal phase of CuMnAs progressively appears as one of the key materials for antiferromagnetic spintronics due to efficient current-induced spin-orbit torques whose existence can be directly inferred from crystal symmetry. Theoretical understanding of spintronic phenomena in this material, however, relies on the detailed knowledge of electronic structure (band structure and corresponding wave functions) which has so far been tested only to a limited extent. We show that AC permittivity (obtained from ellipsometry) and UV photoelectron spectra agree with density functional calculations. Together with the x-ray diffraction and precession electron diffraction tomography, our analysis confirms recent theoretical claim [Phys.Rev.B 96, 094406 (2017)] that copper atoms occupy lattice positions in the basal plane of the tetragonal unit cell., 5 pages, 5 figures + Supplementary Information

We report on the crystal and magnetic structures, magnetic, transport, and thermal properties of ${\mathrm{U}}_{2}{\mathrm{Rh}}_{2}\mathrm{Sn}$ single crystals studied in part in high magnetic fields up to 58 T. The material adopts a ${\mathrm{U}}_{3}{\mathrm{Si}}_{2}$-related tetragonal crystal structure and orders antiferromagnetically below ${T}_{N}=25$ K. The antiferromagnetic structure is characterized by a propagation vector $\mathit{k}=(00\frac{1}{2})$. The magnetism in ${\mathrm{U}}_{2}{\mathrm{Rh}}_{2}\mathrm{Sn}$ is found to be associated mainly with $5f$ states. However, both unpolarized and polarized neutron experiments reveal at low temperatures in zero field non-negligible magnetic moments also on Rh sites. U moments of 0.50(2) ${\ensuremath{\mu}}_{B}$ are directed along the tetragonal axis while Rh moments of 0.06(4) ${\ensuremath{\mu}}_{B}$ form a noncollinear arrangement confined to the basal plane. The response to applied magnetic field is highly anisotropic. Above $\ensuremath{\sim}15\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ the easy magnetization direction is along the tetragonal axis. At lower temperatures, however, a stronger response is found perpendicular to the $c$ axis. While for the $a$ axis no magnetic phase transition is observed up to 58 T, for the field applied at 1.8 K along the tetragonal axis we observe above 22.5 T a field-polarized state. A magnetic phase diagram for the field applied along the $c$ axis is presented.

Magnetic structure of tetragonal UAu$_2$Si$_2$ was investigated by single-crystal neutron diffraction experiments. Below $T_{\rm N}$ = 20 K it orders antiferromagnetically with a propagation vector of $k = (2/3, 0, 0)$ and magnetic moments of uranium ions pointing along the tetragonal $c$-axis. Weak signs of the presence of a ferromagnetic component of magnetic moment were traced out.Taking into account a group theory calculation and experimental results of magnetization and $^{29}$Si-NMR, the magnetic structure is determined to be a squared-up antiferromagnetic structure, with a stacking sequence ($+ + -$) of the ferromagnetic $ac$-plane sheets along the $a$-axis. This result highlights similar magnetic correlations in UAu$_2$Si$_2$ and isostructural URu$_2$Si$_2$., Comment: 7 pages, 7 figures

Single-crystalline UAu$_2$Si$_2$ has been grown by a floating-zone melting method, and its magnetic, thermal and transport properties have been investigated through measurements of magnetization, specific heat and electrical resistivity to reveal its peculiar magnetism. It is shown that UAu$_2$Si$_2$ undergoes a second-order phase transition at \tm = 19 K, which had been believed to be ferromagnetic ordering in the literature, from a paramagnetic phase to an uncompensated antiferromagnetic phase with spontaneous magnetization along the tetragonal $c$-axis (the easy magnetization direction). The magnetic entropy analysis points to the itinerant character of 5f electrons in the magnetic ordered state of UAu$_2$Si$_2$ with large enhancement of the electronic specific heat coefficient of $\gamma$ $\sim$ 150 mJ/K$^2$mol at 2 K. It also reveals the relatively isotropic crystalline electric field effect of this compound, with contrast to the other relative isostructural compounds. The observed magnetization curves strongly suggest that there is a parasitic ferromagnetic component developing below $\sim$ 50 K in high coercivity with the easy axis along the tetragonal $c$-axis. The results are discussed in the context of evolution of magnetism within the entire family of isostructural U$T_2$Si$_2$ compounds., Comment: 13 pages, 21 figures

We report on an experimental and theoretical study of CuMn–V compounds. In agreement with previous works we find low-temperature antiferromagnetism with Neel temperature of 50 K in the cubic half-Heusler CuMnSb. We demonstrate that the orthorhombic CuMnAs is a room-temperature antiferromagnet. Our results are based on X-ray diffraction, magnetization, transport, and differential thermal analysis measurements, and on density-functional theory calculations of the magnetic structure of CuMn–V compounds. In the discussion part of the paper we make a prediction, based on our density-functional theory calculations, that the electronic structure of CuMn–V compounds makes a transition from a semimetal to a semiconductor upon introducing the lighter group-V elements.

The magnetization of a GdMn 6 Sn 6 single crystal has been measured in static magnetic fields up to 14 T as well as in pulsed fields up to 60 T. The easy magnetization direction has been confirmed to lie in the basal plane of the hexagonal crystal, the anisotropy within the plane being negligible. However, our data do not corroborate the earlier assertion that GdMn 6 Sn 6 is a collinear ferrimagnet. This disagrees with the observed field dependence of magnetization along the easy direction as well as with the temperature dependence of spontaneous magnetization. A way out of the contradiction is to admit that GdMn 6 Sn 6 has a more complex, non-collinear magnetic structure.

Solution growth of Gd–Cu–Al resulted in the formation of single crystals of GdCu4Al8 with tetragonal ThMn12-type structure (a = 8.751 Å, c = 5.148 Å), Gd2Cu9.4 – 6.7Al7.6 – 10.3 with hexagonal Th2Zn17-type structure (a = 8.83 Å, c = 1.28 Å), and Gd(Cu, Al)4 with orthorhombic CeNi2+x Sb2 – x -type structure. An antiferromagnetic ordering of GdCu4Al8 was found below 35 K, which is in agreement with the previously reported TN = 35 K and TN = 32 K measured on polycrystalline samples. In the temperature range 50 – 320 K the magnetic susceptibility χ follows the Curie–Weiss law with μeff = 7.8 μB/f. u. and θp = – 17 K for B c, μeff = 7.9 μB/f. u. and θp = – 18 K for B ⊥ c. The a-axis is the easy magnetization direction. The Gd(Cu, Al)4 and Gd(Cu, Al)4 compounds order antiferromagnetically below TN = 35 K and TN = 31 K, respectively.

The magnetization (magnetic susceptibility), specific heat and electrical resistivity of a PrRhIn 5 single crystal were studied. Van Vleck-type paramagnetic behavior and strong magnetocrystalline anisotropy were observed, which is attributed to a strong crystal-field effect on the Pr 3+ ion. A crystal-field effect on the electrical resistivity was observed as well. We focused on the measurement of the specific heat down to low temperatures (down to 0.4 K) in different magnetic fields. Indications of a field-induced transition to the quadrupolar ordered state below 0.4 K were found in the specific-heat data in magnetic fields. First-principles calculations based on density functional theory of the electronic structure and crystal-field interaction were performed in order to better understand the experimental findings.

Many current research efforts in strongly correlated systems focus on the interplay between magnetism and superconductivity. Here we report on coexistence of both cooperative ordered states in recently discovered stoichiometric and fully inversion symmetric heavy fermion compound Ce3PdIn11 at ambient pressure. Thermodynamic and transport measurements reveal two successive magnetic transitions at T1 = 1.67 K and TN = 1.53 K into antiferromagnetic type of ordered states. Below Tc = 0.42 K the compound enters a superconducting state. The large initial slope of dBc2/dT ≈ – 8.6 T/K indicates that heavy quasiparticles form the Cooper pairs. The origin of the two magnetic transitions and the coexistence of magnetism and superconductivity is briefly discussed in the context of the coexistence of the two inequivalent Ce-sublattices in the unit cell of Ce3PdIn11 with different Kondo couplings to the conduction electrons.

CeCu0.7Al3.3 single crystals have been prepared by the solution growth method. The compound crystallizes in the tetragonal BaAl4-type of structure with lattice parameters a=4.262 Aand c=10.776 A. A detailed specific-heat study of CeCu0.7Al3.3 is presented. The data confirm ferromagnetic order below TC=4 K. The estimated Kondo temperature lies also around 4 K. The electronic specific-heat coefficient was found to be moderately enhanced over the values for common metallic compounds. It is shown that the energy splitting between the ground state and the first excited doublet amounts to 75 K at least, which is considerably higher than the value deduced from magnetization data.

Magnetization behavior and Hall resistivity of YMn 6 Sn 6 , which crystallizes in the hexagonal HfFe 6 Ge 6 -type of structure, have been investigated on single crystals at various temperatures in the ordered magnetic state. The field dependence of the Hall resistivity shows anomalies, which are related to the field-induced spin reorientations occurring in YMn 6 Sn 6 . It is also found that the Hall resistivity cannot simply be described by the anomalous contribution proportional to the magnetization, but that an additional field-dependent contribution is present.

A Comment on the Letter by D. Kaczorowski et al., Phys. Rev. Lett. 103, 027003 (2009). The authors of the Letter offer a Reply.

Solution growth of single crystals of the recently reported new compound Ce2PdIn8 was investigated. When growing from a stoichiometry in a range 2:1:20 - 2:1:35, single crystals of CeIn3 covered by a thin (~50 um) single-crystalline layer of Ce2PdIn8 were mostly obtained. Using palladium richer compositions the thickness of the Ce2PdIn8 layers were increased, which allowed mechanical extraction of single-phase slabs of the desired compound suitable for a thorough study of magnetism and superconductivity. In some solution growth products also CePd3In6 (LaNi3In6 - type of structure) and traces of phases with the stoichiometry CePd2In7, Ce1.5Pd1.5In7 (determined only by EDX) have been identified. Magnetic measurements of the Ce2PdIn8 single crystals reveal paramagnetic behaviour of the Ce3+ ions with significant magnetocrystalline anisotropy. Above 70 K the magnetic susceptibility follows the Curie-Weiss law with considerably different values of the paramagnetic Curie temperature, for the magnetic field applied along the a- (-90 K) and c-(-50 K) axis. Below the reported critical temperature for superconductivity Tc (0.69 K) the electrical resistivity drops to zero. Comparative measurements of the electrical resistivity, heat capacity and AC susceptibility of several crystals reveal that the superconducting transition is strongly sample-dependent., submitted (2Nov09) to Intermetallics

A GdNi single crystal has been prepared by the Czochralski method and studied by measuring the magnetization, electrical resistivity and thermal expansion. The ferromagnetic ordering below T C =69 K has been confirmed. The saturated magnetization at 2 K was found to be identical (7.2 μ B /f.u.) along all the three principal crystallographic directions. This result is in agreement with theoretical calculations, which yield magnetic moment of 7.0 μ B /f.u. for Gd 3+ ion and 0.18 μ B /f.u. for conduction electrons with magnetic moment of the same direction as the Gd moment. An anomalous spontaneous magnetostriction is dominating the thermal expansion behavior below T C . In particular, we have observed a large contraction in the c -direction and a smaller expansion in the a and b directions (nearly identical). The unit cell volume expands below T C (Δ V / V =8×10 −4 ). The observed anisotropy of the magnetostriction in GdNi is attributed to anisotropic magnetoelastic coupling.

CePt 3 C has been synthesized and studied by powder X-ray diffraction (at RT), specific heat, resistivity and magnetization measurements at temperatures from RT down to 0.4 K and in magnetic fields up to 10 T. A possible scenario for the ground state of CePt 3 C based on the observed phenomena is proposed.

U 3 Co 4 Ge 7 and U 3 Co 2 Ge 7 have been prepared as single crystals by the solution growth method from tin flux and studied by X-ray diffraction, magnetic, transport, and specific-heat measurements; ab initio electronic-structure calculations have also been performed to study magnetism theoretically. U 3 Co 4 Ge 7 has a tetragonal structure ( I 4/ m m m ), while U 3 Co 2 Ge 7 crystallizes in en orthorhombic structure ( C m m m ), which appears to be a distortion of a tetragonal structure. All measurements document ferromagnetism in U 3 Co 4 Ge 7 below T C = 21 K with a strong magnetocrystalline anisotropy. The c -axis has a strong ferromagnetic contribution to magnetization and was found to be the easy-magnetization direction. U 3 Co 2 Ge 7 orders magnetically below 40 K; the magnetic structure is sensitive to the ratio a / c ≈1, e.g., the deviation from the tetragonal axis.

U3Co4Ge7 and U3Co2Ge7 have been prepared as single crystals by solution growth from tin flux. U3Co4Ge7 crystallizes in the tetragonal structure (I4/mmm) with lattice parameters a = 0,4116 nm and c = 2,749 nm and U3Co2Ge7 possesses the orthorhombic structure (Cmmm) with a = 0,4151 nm, b = 2,498 nm, c = 0,4160 nm. All measurements document ferromagnetism in U3Co4Ge7 below TC = 21 K. The magnetization and magnetic susceptibility measurements revealed strong magnetocrystalline anisotropy. The c-axis has a strong ferromagnetic contribution to the magnetization and was found to be the easy-magnetization direction. U3Co2Ge7 shows onset of magnetic ordering at 41 K. The b-axis is the easy magnetization direction with the saturated magnetization μat = 1 μB/U at 2 K. The magnetization curves show anomalous behavior; the virgin curve goes far out of the hysteresis loop and reaches higher value of saturated magnetization.