CrSiTe₃ has attracted recent interest as a candidate single-layer ferromagnetic semiconductor, but relatively little is known about the bulk properties of this material. Here, we report single-crystal X-ray diffraction, magnetic properties, thermal conductivity, vibrational, and optical spectroscopies and compare our findings with complementary electronic structure and lattice dynamics principles calculations. The high temperature paramagnetic phase is characterized by strong spin-lattice interactions that give rise to glassy behavior, negative thermal expansion, and an optical response that reveals that CrSiTe₃ is an indirect gap semiconductor with indirect and direct band gaps at 0.4 and 1.2 eV, respectively. Measurements of the phonons across the 33 K ferromagnetic transition provide additional evidence for strong coupling between the magnetic and lattice degrees of freedom. The Si-Te stretching and Te displacement modes are sensitive to the magnetic ordering transition, a finding that we discuss in terms of the superexchange mechanism. Spin-lattice coupling constants are also extracted.

Intrinsic, two-dimensional ferromagnetic semiconductors are an important class of materials for overcoming the limitations of dilute magnetic semiconductors for spintronics applications. ${\text{CrSiTe}}_3$ is a particularly interesting member of this class, since it can likely be exfoliated down to single layers, where $T_C$ is predicted to increase dramatically. Establishing the nature of the magnetism in the bulk is a necessary precursor to understanding the magnetic behavior in thin-film samples and the possible applications of this material. In this work, we use elastic and inelastic neutron scattering to measure the magnetic properties of single-crystalline ${\text{CrSiTe}}_3$. We find that there is a very small single ion anisotropy favoring magnetic ordering along the $c$ axis and that the measured spin waves fit well to a model where the moments are only weakly coupled along that direction. Finally, we find that both static and dynamic correlations persist within the $ab$ plane up to at least 300 K, strong evidence of this material's two-dimensional characteristics that are relevant for future studies on thin-film and monolayer samples.

Recent high-pressure studies found that structural/magnetic phase transitions are very pressure sensitive in ${\text{CaFe}}_2{\text{As}}_2$ and that superconductivity can be achieved under modest pressure, although details of the sharpness and temperature of transitions vary between liquid medium and gas medium measurements. To better understand this issue, we performed high-pressure susceptibility and transport studies on ${\text{CaFe}}_2{\text{As}}_2$, using helium as the pressure medium. The signatures of the transitions to the low-temperature orthorhombic and collapsed tetragonal phases remained exceptionally sharp, and no signature of bulk superconductivity was found under our hydrostatic conditions. Our results suggest that superconductivity in ${\text{CaFe}}_2{\text{As}}_2$ is associated with a low-temperature, multicrystallographic-phase sample that is the result of nonhydrostatic conditions associated with the combination of a first-order structural phase transition and frozen liquid media.

In a prototypical ferromagnet (Ga,Mn)As based on a III–V semiconductor, substitution of divalent Mn atoms into trivalent Ga sites leads to severely limited chemical solubility and metastable specimens available only as thin films. The doping of hole carriers via (Ga,Mn) substitution also prohibits electron doping. To overcome these difficulties, Masek et al. theoretically proposed systems based on a I–II–V semiconductor LiZnAs, where isovalent (Zn,Mn) substitution is decoupled from carrier doping with excess/deficient Li concentrations. Here we show successful synthesis of Li_1+y(Zn_1−xMn_x)As in bulk materials. Ferromagnetism with a critical temperature of up to 50 K is observed in nominally Li-excess (y=0.05–0.2) compounds with Mn concentrations of x=0.02–0.15, which have p-type metallic carriers. This is presumably due to excess Li in substitutional Zn sites. Semiconducting LiZnAs, ferromagnetic Li(Zn,Mn)As, antiferromagnetic LiMnAs, and superconducting LiFeAs systems share square lattice As layers, which may enable development of novel junction devices in the future.