Magnetic anisotropy in van-der-Waals ferromagnet VI3

A comprehensive study of magnetocrystalline anisotropy of a layered van-der-Waals ferromagnet VI3 was performed. We measured angular dependences of the torque and magnetization with respect to the direction of the applied magnetic field within the "ac" plane perpendicular to and within the basal ab plane, respectively. A two-fold butterfly-like signal was detected by magnetization in the perpendicular "ac" plane. This signal symmetry remains conserved throughout all magnetic regimes as well as through the known structural transition down to the lowest temperatures. The maximum of the magnetization signal and the resulting magnetization easy axis is significantly tilted from the principal c axis by ~40{\deg}. The close relation of the magnetocrystalline anisotropy to the crystal structure was documented. In contrast, a two-fold-like angular signal was detected in the paramagnetic region within the ab plane in the monoclinic phase, which transforms into a six-fold-like signal below the Curie temperature TC. With further cooling, another six-fold-like signal with an angular shift of ~30{\deg} grows approaching TFM. Below TFM, in the triclinic phase, the original six-fold-like signal vanishes, being replaced by a secondary six-fold-like signal with an angular shift of ~30{\deg}.Comment: 14 pages, 10 figure

Enhanced triplet superconductivity in next generation ultraclean UTe2

The spin-triplet superconductor UTe$_2$ exhibits a myriad of exotic physical phenomena, including the possession of three distinct superconducting phases at ambient pressure for magnetic field $\mu_0 H \leq$ 40 T aligned in certain orientations. However, contradictory reports between studies performed on UTe$_2$ specimens of varying quality have severely impeded theoretical efforts to understand the microscopic properties of this material. Here, we report high magnetic field measurements on a new generation of ultraclean UTe$_2$ specimens, which possess enhanced superconducting critical temperatures and fields compared to previous sample generations. Remarkably, for $H$ applied close to the hard magnetic $b$ direction, we find that the angular extent of magnetic field-reinforced superconductivity is significantly increased in these high purity crystals. This suggests that, in proximity to a field-induced metamagnetic transition, the enhanced role of magnetic fluctuations - that are strongly suppressed by disorder - is likely responsible for tuning UTe$_2$ between two distinct spin-triplet superconducting phases. Our results reveal a strong sensitivity to crystalline disorder of the field-reinforced superconducting state of UTe$_2$

Effect of Si Substitution and Annealing on Magnetocaloric Properties in TbCo2TbCo_2

We report on magnetocaloric properties of the as-cast and annealed $TbCo_2$ with partial substitution of cobalt by silicon. The samples were characterized by powder X-ray diffraction and investigated by heat capacity measurements (8-300 K, in fields 0 T and 1 T). $TbCo_2$ undergoes a second-order type phase transition at $T_C$ = 240 K, from paramagnetic to ferrimagnetic state;similar behavior was revealed in the Si-doped compounds. The temperature dependence of magnetic entropy and the corresponding magnetocaloric effect were derived for all studied samples. The influence of the heat treatment and Si doping on magnetocaloric properties will be discussed in context of the analogue case $Er(Co_{1-x}Si_x)_2$

Effect of Si Substitution and Annealing on Magnetocaloric Properties in TbCo 2

We report on magnetocaloric properties of the as-cast and annealed $TbCo_2$ with partial substitution of cobalt by silicon. The samples were characterized by powder X-ray diffraction and investigated by heat capacity measurements (8-300 K, in fields 0 T and 1 T). $TbCo_2$ undergoes a second-order type phase transition at $T_C$ = 240 K, from paramagnetic to ferrimagnetic state;similar behavior was revealed in the Si-doped compounds. The temperature dependence of magnetic entropy and the corresponding magnetocaloric effect were derived for all studied samples. The influence of the heat treatment and Si doping on magnetocaloric properties will be discussed in context of the analogue case $Er(Co_{1-x}Si_x)_2$

Low magnetic field phase diagram of UCoGe

We propose an alternate scenario for the relation between ferromagnetism FM and superconductivity SC in UCoGe at ambient pressure. On the basis of neutron polarimetry measurement performed in strictly zero field on a single crystal at ambient pressure, we claim that the SC phase does exist in spite of lack of long range FM order. Moreover, the SC regime dominates to the paramagnetic state in small external magnetic fields. Above the critical SC temperature, TSC 0.64 K, the zero field state is characterized by a regime with strong FM spin fluctuations, suggesting the proximity of the FM quantum critical poin

Double phase transition and magnetic ordering in NdFe2Si2 single crystal

We have investigated a single crystal of NdFe2Si2 by variety of macro and microscopic experiments in wide range of temperatures and magnetic fields. The results confirmed antiferromagnetic ordering below the N el temperature TN amp; 8776;14 K and uniaxial magnetocrystalline anisotropy with easy magnetization direction along the c axis. Specific heat and dilatometry data exhibit an additional sharp anomaly below the TN, in particular at Tt 13.1 K, which was tentatively considered as a signature of an order order magnetic phase transition. The neutron diffraction experiment, however, reveals no evidence of an order order magnetic phase transition and confirms existence of only one magnetic structure up to the TN with propagation vector . The temperature dependence of the electrical resistivity shows only a single anomaly at TN , consistently with neutron diffraction results. Furthermore, comprehensive neutron diffraction experiment is scheduled