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Polycrystalline samples of UCoGe doped by 1% and 5% of Fe, Ni, and Ru, respectively, have been prepared. Magnetization, ac susceptibility, and electrical resistivity measurements were done on samples in as cast state and annealed at 900 °C for 10 days. The TiNiSi-type orthorhombic crystal structure proved by x-ray powder diffraction was confirmed in the whole series of compounds. Except for the 1% Ni doped sample, all the other samples exhibit clear spontaneous ferromagnetism. The 5% doped compounds have the Curie temperature of TC=6.5 K for U(Co,Fe)Ge, TC=5.0 K for U(Co,Ni)Ge, and TC=7.5 K for U(Co,Ru)Ge. All the studied compounds exhibit only small spontaneous magnetic moments around 0.04μB at 1.8 K. The increasing TC value and stabilization of magnetic moments induced by the transition metals doping are accompanied by a shift in the superconducting transition to lower temperatures with respect to pure UCoGe (TSC≈0.7 K). The 5% doped samples show no sign of superconductivity down to T=0.4 K. [ABSTRACT FROM AUTHOR]

In this paper, we report the results of an ambient and high pressure study of a 5f-electron ferromagnet URhGa. The work is focused on measurements of magnetic and thermodynamic properties of a single crystal sample and on the construction of the p-T phase diagram. Diamond anvil cells were employed to measure the magnetization and electrical resistivity pressures up to ∼ 9 GPa. At ambient pressure, URhGa exhibits collinear ferromagnetic ordering of uranium magnetic moments μU ∼ 1.1 μB (at 2 K) aligned along the c-axis of the hexagonal crystal structure below the Curie temperature TC = 41K. With the application of pressure up to 5GPa the ordering temperature TC initially increases whereas the saturated moment slightly decreases. The rather unexpected evolution is put in the context of the UTX family of compounds. [ABSTRACT FROM AUTHOR]

We investigate the discontinuous ferromagnetic phase diagram near tricritical point in UCo1-xRuxAl compounds by electrical resistivity measurements. Separation of phases in UCo0.995Ru0.005Al at ambient pressure and in UCo0.990Ru0.010Al at pressure of 0.2 GPa and disappearance of ferromagnetism at 0.4 GPa is confirmed. The exponent of temperature dependence of electrical resistivity implies change from Fermi liquid-like behavior to non-Fermi liquid at 0.2 GPa and reaches minimum at 0.4 GPa. Our results are compared to results obtained on the pure UCoAl and explanation for different exponents is given. [ABSTRACT FROM AUTHOR]

Abstract: The influence of pressure on the formation of U magnetic moments and mediation of exchange interactions are two principal aspects of the complex role of the 5f-ligand hybridization in magnetism of U intermetallics. Application of external pressure yields changes of interatomic distances, which are the crucial parameters controlling the hybridization. We report on pressure experiments with a 5f-electron ferromagnet UPtAl (T C=42.5K, M s=1.4 μ B/f.u. at ambient pressure). Application of hydrostatic pressure up to 1GPa yields decrease of the spontaneous magnetization M s with a rate dM s/dp=−0.027 μ B/GPa, whereas T C increases (dT C/dp=2.5K/GPa). Extension of the electrical resistivity measurements of UPtAl to pressures up to 22GPa reveals that the initial increase of T C with pressure continues up to 6GPa, where T C reaches the maximum value, and decreases with further increasing pressure. The drastic change of the R(T) curve at 17GPa is presumably connected with suppression of ferromagnetism in UPtAl. [Copyright &y& Elsevier]

Abstract: Magnetization behavior and Hall resistivity of YMn6Sn6, which crystallizes in the hexagonal HfFe6Ge6-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 YMn6Sn6. 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. [Copyright &y& Elsevier]

Abstract: The temperature dependence of the specific heat of the itinerant 5f-electron antiferromagnet UIrGe was studied on a single crystal in magnetic fields up to 14T applied along the principal crystallographic directions. For fields along the c-axis, evolution of T N-related magnetic specific heat (magnetic entropy) anomaly is compared with the corresponding magnetization steps. [Copyright &y& Elsevier]

When a magnetic field is applied along the b-axis of the orthorhombic structure (TiNiSi-type) of CePtSn at temperatures below 3 K a sharp drop of resistance is observed when sweeping field up around 3 T. The original zero-field resistance is, however, not recovered when sweeping the field down through this critical field. Zero field neutron diffraction data reveal two propagation vectors q = (0, δ, 0) with δ1=0.469 and δ2=0.427 coexisting below 3 K. The field induced negative irreversible GMR effect around 3 T is found coinciding with suppression of the ‘δ2’ intensity in favor of the increasing ‘δ1’ one. A possible scenario for these phenomena will be discussed. [Copyright &y& Elsevier]

UCoGe is an archetype of coexisting weak itinerant 5f-electron ferromagnetism (TC ~ 3 K,μs = 0:03μB/f.u.) and superconductivity (TSC ~ 0:6 K) at ambient pressure. The Ru substitution for Co leads to an initial sharp increase of the TC up to the maximum of TC = 8:5 K for x = 0:12, increase of spontaneous magnetic moment and suppression of superconductivity. We have grown the UCo0:88Ru0:12Ge single crystal and studied magnetization along the principal crystallographic axes. To see the microscopic background of these findings we performed a polarized neutron diffraction experiment on D3 diffractometer in ILL. We have found that the Co and U moments are parallel in UCo0:88Ru0:12Ge, in contrast to the antiparallel configuration in UCoGe. This is probably the reason of the spontaneous magnetization increase with Ru doping. [ABSTRACT FROM AUTHOR]

We report on the investigation of recently discovered heavy fermion compounds within the Ce-Pd-In system. Single crystals of CenPdmIn3n+2m (n = 2,3,5; m = 1,2) and Ce4Pd10In21 were synthesized from In-fhix. Specific heat measurements of the multiphase CenPdmIn3n+2m system revealed a superconducting transition at Tc = 0.69 K arising from Ce2Pdln8 and another, magnetic transition at Tm = 1.67 K arising from either Ce3Pdln11 or Ce5Pd2In19. Low-temperature data of Ce4Pd10In21 display ferromagnetic long-range order below 0.8 K. [ABSTRACT FROM AUTHOR]

Abstract: A computational model for the calculation of the bulk magnetic properties of rare-earth ferrimagnets and antiferromagnets was developed and justified theoretically in the framework of mean-field theory. To demonstrate its utility, the model was applied to calculate the anisotropic Heisenberg exchange constants of CeTe2 by fitting magnetization curves numerically, and to derive analytical expressions for the spontaneous magnetization as well as the Neél temperature by considering only the crystal-field (CF) ground-state doublet. It turns out that the temperature dependencies of the magnetization and the specific heat calculated with the formulas in absence of an external field are identical with the plots obtained directly with the full lowest CF J-multiplet, manifesting the strong role of the Kramers doublet in the magnetic process at low temperatures. Finally, the model was applied to investigate the effects of the quadrupolar and magneto-elastic (QM) interactions on the magnetic properties of the system. [Copyright &y& Elsevier]

The ErNi1-xCuxAl compounds have been studied from the view of crystallographic structure and magnetic properties by means of X-ray and neutron diffraction, magnetization and heat capacity measurements. The hexagonal ZrNiAl-type crystal structure adopted by the parent compounds ErNiAl and ErCuAl is conserved over the entire composition range. The concentration dependence of lattice parameters shows a discontinuity between x=0.5 and 0.6 both in paramagnetic and magnetically ordered phase. The evolution of magnetism from antiferromagnetism (AF) with Er-moments within the basal plane in ErNiAl to the simple ferromagnetism (F) with moments along the c-axis in ErCuAl is rather complex. The AF ordering is characterized by a propagation vector (1/2,0,1/2) with moments within the basal plane in the low Cu-concentration region for x up to 0.40. An incommensurate component with Er-moments along c develops within the range of 0.20⩽x⩽0.40 and grows on account of the commensurate one. The ErNi0.5Cu0.5Al is a simple F with moments along c. For concentrations with x=0.6 and 0.8 signs of short-range ordering were revealed. [Copyright &y& Elsevier]

A single crystal of the UCoAl0.75Sn0.25 quasiternary compound has been grown and studied by measuring the magnetization, specific heat and electrical resistivity at various temperatures and magnetic fields. Similar to the parent compounds UCoAl and UCoSn, the magnetization of their solid solution exhibits uniaxial anisotropy with a strong magnetic response along the c-axis and a weak and nearly temperature independent paramagnetic signal in the basal plane. The evolution of the c-axis magnetization isotherms, as well as the anomalies in the temperature dependence of the specific heat and resistivity point to ferromagnetism in UCoAl0.75Sn0.25 below TC≈5.5 K. The low value of the spontaneous magnetic moment, poor saturation of the magnetization, the pronounced negative magnetoresistance with increasing magnetic field and the temperature and magnetic field dependence of specific heat provide indications of strong fluctuations of the U magnetic moment also in the ferromagnetic state. [Copyright &y& Elsevier]

We report the single crystal properties of CePd 2 Zn 3 and CePd 2 Ga 3 compounds. The compounds were prepared by Bridgman method in high-frequency induction furnace. Both compounds adopt the hexagonal PrNi 2 Al 3 -type structure with a = 5.3914(2) Å, c = 4.3012(2) Å for CePd 2 Zn 3 and a = 5.4106(8) Å, c = 4.2671(8) Å for CePd 2 Ga 3 , respectively. CePd 2 Zn 3 orders antiferromagnetically below T N = 1.9 K. Magnetoresistance measurements revealed a crossover at B c = 0.95 T. CePd 2 Ga 3 orders ferromagnetically at T C = 6.7 K. Applied hydrostatic pressure reduces the value of the Curie-temperature (rate ∂ T C / ∂ p = 0.9 K GPa − 1 ) down to 3.9 K at 3.2 GPa. Both compounds display a strong magnetocrystalline anisotropy with easy axis of magnetization perpendicular to the c -axis in the hexagonal lattice. [ABSTRACT FROM AUTHOR]

A thorough investigation is presented of the magnetic and structural properties of Mn-doped Bi 2 Se 3 topological insulators grown by molecular beam epitaxy on top of insulating BaF 2 (111) substrates. The magnetic properties have been studied in the temperature range from 2 K to 300 K in magnetic fields up to 7 T. The systems were further characterized by means of high-resolution X-ray diffraction, electron-microprobe analysis, and X-ray photoemission spectroscopy. Samples with the atomic concentration of Mn up to about 0.06 exhibit an almost perfect crystalline structure while, for higher Mn concentrations, diffuse scattering from defects is observed. Photoemission results suggest a localized non-metallic Mn 3d 5 ground state which is weakly or intermediately coupled to the Bi 2 Se 3 environment. The exchange interaction between the Mn moments leads to a ferromagnetic phase at low temperatures with a roughly linear relation between the Curie temperature and the atomic concentration of Mn. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic behavior of the compound DyMn6Ge6 has been studied on single crystals that have been prepared in an In flux. The compound orders antiferromagnetically at about 450K and exhibits very complex magnetic properties in the magnetically ordered state. The evolution of the magnetization in the ordered state as a function of temperature and the magnetization processes has been investigated at various temperatures in fields up to 14T. At 4.2K, where higher magnetic fields were needed, measurements of the magnetization have been carried out in pulsed fields up to around 50T. [Copyright &y& Elsevier]

Despite belonging to a well-studied family of transition metal trihalides, VI 3 has received significant attention only recently. As a hard ferromagnetic van der Waals compound with a large coercivity, it attracted much attention because of its potential use in atomically thin spintronic and optoelectronic devices. However, practical exploration of VI 3 is challenging due to its instability under ambient conditions. Here, we present a comprehensive set of optical, x-ray diffraction, magnetization, and ellipsometric measurements of VI 3 and demonstrate that, similarly to the related van der Waals ferromagnet CrI 3 , the degradation process is accelerated by the presence of moisture. The VI 3 surface was covered by selected media commonly used in physical measurements to test its stability and lower the degradation rate three times or higher, providing practical information for experimentalists interested. The decomposition study at ambient conditions shows that the VI 3 single crystal can be used for most of the bulk, magnetization, and optical measurements without any noticeable change of physical properties, as the significant degradation appears first after ∼2 h of exposition as illustrated, e.g., by the evolution of the ferromagnetic T 1 and T 2 transitions. The ellipsometric measurement demonstrates that even the surface remains optically stable for at least 5 min. • The degradation of VI 3 is accelerated by the presence of moisture, similarly to CrI 3. • VI 3 crystals are stable for most of the bulk experiments after a 2 h-exposition. • Ellipsometry shows that the surface remains optically stable for at least 5 min. [ABSTRACT FROM AUTHOR]

Abstract: The intermetallic compound UGa1.85Zr0.15 does not crystallize in the AlB2 structure shared by UGa2 and UZr2. Instead, it forms in the same orthorhombic structure as U3Ga5 (Pu3Pd5 type), but the somewhat smaller lattice parameters reduce the unit cell volume by 2.1% with respect to U3Ga5. Basic magnetic properties, namely the ferromagnetic ground state below T C =23K, are similar to U3Ga5. A more detail study of magnetic properties reveals interesting metamagnetic behavior with a critical field of 2–3T, which increases with increasing temperature. The high γ-value of 110mJmol−1 K−2 points to a narrow 5f band at Fermi level. [Copyright &y& Elsevier]

Abstract: Specific heat of a single crystalline URhSi was measured by a relaxation method in a temperature range 0.3–25K in magnetic fields up to 8T applied along the two of the principal axes. The low-temperature specific heat exponentially decays with magnetic field. The decay is much faster in fields applied along the easy magnetization direction (the c-axis) than for the hard axis (the a-axis) case. A strong upturn in c p /T versus T below 0.6K that disappears with application of magnetic field is observed suggesting possible magnetic or superconducting phase transition at lower temperatures. The electrical resistivity in the vicinity of the ferromagnetic phase temperature is found to be reduced by more than 50% upon application of magnetic field of 8T applied along the c-axis. URhSi represent an itinerant ferromagnetic system with influence of spin fluctuations. [Copyright &y& Elsevier]

Abstract: Substitution of Y for U in the itinerant 5f-electron metamagnet, UCoAl, transforms the system to a ferromagnetic state. Application of external hydrostatic pressure above 0.3GPa suppresses the ferromagnetism and restores the “UCoAl-type” metamagnetism back. However, the metamagnetic transition becomes of the second order instead of the first order one in parent UCoAl. This is attributed to enhancement of fluctuations of the U magnetic moment upon dilution of the U sublattice. [Copyright &y& Elsevier]

Abstract: Results of magnetization (M), AC-susceptibility , specific heat (C) and electrical-resistivity measurements on DyFe2Si2 single crystals are reported and analyzed in conjunction with first-principles electronic-structure calculations. Clear anomalies in the , and dependences indicate a magnetic-phase transition (paramagnetic ↔ antiferromagnetic) at 3.8K. Magnetic and specific-heat data obtained in magnetic fields (B) manifest uniaxial magnetocrystalline anisotropy with the easy magnetization direction along the c-axis of the tetragonal structure. These findings together with the metamagnetic transition observed on the curve measured at 2K and the evolution of the specific-heat anomaly at 3.8K in a magnetic field applied along the c-axis corroborate a scenario for the physics of DyFe2Si2 in terms of antiferromagnetism with Néel temperature . The first-principles electronic-structure calculations confirm the absence of an ordered Fe moment, which is in agreement with previously reported experimental findings. The magnetization isotherms and the temperature dependences of the specific heat and paramagnetic susceptibility in the paramagnetic state were analyzed taking into account the crystal-field interaction. The experimentally determined crystal-field parameters are compared with the results of first-principles crystal-field calculations. [Copyright &y& Elsevier]

The hexagonal compound UCuGe, an antiferromagnet with TN=48 K, exhibits in fields 38–45 T (at 4.2 K), applied along the c-axis, a spin-flop transition to a state with a moment of 1.35μB/U. The magnetic susceptibility in fields applied along the basal plane is considerably higher than along the c-axis but no transition occurs in fields up to 42 T applied along either the 〈1 0 0〉 or 〈1 2 0〉 axis. The irreversible (magnetic history dependent) magnetization anomaly observed around 15 T (at 4.2 K) is attributed to repopulation of antiferromagnetic domains. [Copyright &y& Elsevier]

We present the temperature and magnetic-field dependencies of the c-axis magnetization of a UCoAl single crystal under various uniaxial pressures exerted along the c-axis. The main result obtained is the uniaxial-pressure-induced reduction of the critical field of the metamagnetic transition followed by the formation of ferromagnetism at higher uniaxial-pressures. These and other associated results are discussed in comparison with corresponding data obtained by applying hydrostatic pressure on the same material. A scenario considering a variation of the anisotropic 5f-ligand hybridization and its consequences induced by the two different types of applied pressure is an important base for the discussion. The pressure-induced variations of the 5f–3d hybridization within the basal plane of the ZrNiAl-type hexagonal structure seem to be the underlying aspect of the evolution of the magnetism in UCoAl. [Copyright &y& Elsevier]

Abstract: Magnetization, susceptibility and resistivity were measured on the (antiferromagnetic with ) single crystal along both principal crystallographic axes in the temperature range 2–300K and in magnetic fields up to 14T. Magnetic properties were found to be isotropic. The susceptibility obeys the Curie–Weiss law with the effective magnetic moment A saturated moment of was determined at 2K. On the other hand, resistivity and magnetoresistivity are anisotropic and show an anomaly at . The anomalies in the susceptibility and resistivity data at are associated with the magnetic phase transition. [Copyright &y& Elsevier]

Abstract: 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=69K has been confirmed. The saturated magnetization at 2K 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 Gd3+ 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 (ΔV/V=8×10−4). The observed anisotropy of the magnetostriction in GdNi is attributed to anisotropic magnetoelastic coupling. [Copyright &y& Elsevier]

Abstract: We present results of magnetic and specific-heat study of polycrystalline and single-crystalline samples of the CeT2Si2 compounds (T=Au, Ag). The CeAu2Si2 single crystal shows, for a field applied along the c-axis, a field-induced transition at approx. 2T, whereas there is no sign for the transition on the magnetization curve for the field applied along the a-axis. The CeAg2Si2 compound shows no such anisotropic behavior on magnetization curves; only for the field applied along the c-axis there is a signature of a ground state characterized by small spontaneous moment (ferromagnetic component). The AC response is robust to frequency of the applied AC magnetic field in the case of CeAu2Si2, whereas the AC susceptibility of CeAg2Si2 shows moderate frequency dependence. [Copyright &y& Elsevier]