Ferromagnetism in two-dimensional CrTe2epitaxial films down to a few atomic layers

Two-dimensional (2D) van der Waals ferromagnetic materials have attracted intense attention due to their potential impact on both fundamental and applied research studies. Recently, a new 2D ferromagnet CrTe2, prepared by mechanical exfoliation or chemical vapor deposition, has gained interest due to its novel magnetic properties. In this work, high quality CrTe2 epitaxial thin films were prepared on GaAs (111)B substrates using solid source molecular beam epitaxy, with the thickness varying from 35 to 4 monolayers (MLs). The magnetic easy axis of all the films is oriented along the c-axis. A Curie temperature of 205 K is found in the 35 ML CrTe2 film, measured by the temperature-dependent anomalous Hall resistance (RAHE). Importantly, even when the film thickness decreases to 4 MLs, a robust out-of-plane ferromagnetism with a Curie temperature of 191 K has been demonstrated. This finding could pave the way for investigating the fundamental studies in 2D ferromagnetism and has great significance in device applications

Thermal induced spin-polarized current protected by spin-momentum locking in nanowires

Spin-momentum locking arising from strong spin-orbit coupling is one of the key natures of topological materials. Since charge can induce a spin polarization due to spin-momentum locking, the search for materials that exhibit this feature has become one of the top priorities in the field of spintronics. In this paper, we report the electrical detection of the spin-transport properties of nanowires, using a nonlocal geometry measurement. A clear hysteresis voltage signal, which depends on the relative orientations between the magnetization of the ferromagnetic electrodes and the carrier spin polarization, has been observed. The hysteresis voltage states can be reversed by altering the electron movement direction, providing direct evidence of the spin-momentum locking feature of nanowires and revealing its topological nature. Furthermore, the current-dependent measurement suggests that the charge (spin) current is induced by thermal effect, which utilizes the thermoelectric properties of . Using the thermal effect to control the spin-polarized current protected by spin-momentum locking offers possibilities for small-sized devices based on the topological materials

Switching on antiferromagnetic coupled superparamagnetism by annealing ferromagnetic Mn/CdS nanoparticles

Mixed phases of metastable cubic and stable hexagonal manganese assisted CdS nanoparticles were synthesized by a colloidal route. These phases were quantified by the Short and Steward method of X-ray diffraction and differential scanning calorimetry analysis. The photoluminescence (PL) emission observed around ∼ 550 nm for undoped CdS is found to be due to cadmium vacancy defects; on increased addition of Mn2+ both the intensity and the line width of this emission continuously but disproportionately decrease and a new emission around ∼ 585 nm, interpreted to be due to manganese d–d emission, emerges with increased intensity but with no change in line width. The disproportionate decrease in the area and bandwidth of the ∼ 550 nm emission reveals that the intensity decrease is not a manifestation of the line width change. This decrease in intensity, i.e., the transition probability, is attributed to both the quenching effect by manganese and reduction in Cd vacancy defects due to substitution by Mn2+. The enriched 5% Mn/CdS was subjected to annealing in order to find out any possible changes or transformation during the annealing proces. An increase in the electron paramagnetic resonance intensity of preannealed sample on lowering temperature, much more than suggested by the Boltzmann population difference, indicates it to be ferromagnetic. On the other hand, postannealed sample exhibits antiferromagnetic coupled superparamagnetism as revealed by a drastic reduction in intensity down to the Néel temperature (TN) with unaltered line width and a substantial decrease in line width below TN. This conversion from ferromagnetism to antiferromagnetic coupled superparamagnetism after annealing is strongly supported by magnetic measurements, in which the preannealed sample exhibits increased coercivity on lowering the temperature, a case of ferromagnetism, and the postannealed material, however, exhibits low coercivity along with exchange bias below TN, representing superparamagnetism. This conversion is due to ionic migration of Mn2+ as supported by magnetic and PL measurements. High-resolution transmission electron microscopy confirms the morphology and size of nanoparticles

Calorimetric Study on EuCoGe 3 and EuRh 2 In 8 under Pressure

International audienc

Calorimetric Study on EuCoGe 3 and EuRh 2 In 8 under Pressure

International audienc