arXiv subjects

Suhan Son

Publications and source records attributed to Suhan Son.

21 records · Page 2Linked to original sources

arXiv2019

Crystal Structures and Phase Transitions of the van-der-Waals Ferromagnet VI3

The results of a single-crystal X-ray-diffraction study of the evolution of crystal structures of VI3 with temperature with emphasis on phase transitions are presented. Some related specific-heat and magnetization data are included. The existence of the room-temperature trigonal crystal structure R-3 (148) has been confirmed. Upon cooling, VI3 undergoes a structural phase transition to a monoclinic phase at Ts ~ 79 K. Ts is reduced in magnetic fields applied along the trigonal c-axis. When VI3 becomes ferromagnetic at TFM1 ~ 50 K, magnetostriction-induced changes of the monoclinic-structure parameters are observed. Upon further cooling, the monoclinic structure transforms into a triclinic variant at 32 K which is most likely occurring in conjunction with the previously reported transformation of the ferromagnetic structure. The observed phenomena are preliminarily attributed to strong magnetoelastic interactions.

cond-mat.str-el↗

arXiv2019

Antiferromagnetic ordering in van der Waals two-dimensional magnetic material MnPS3 probed by Raman spectroscopy

Magnetic ordering in the two-dimensional limit has been one of the most important issues in condensed matter physics for the past several decades. The recent discovery of new magnetic van der Waals materials heralds a much-needed easy route for the studies of two-dimensional magnetism: the thickness dependence of the magnetic ordering has been examined by using Ising- and XXZ-type magnetic van der Waals materials. Here, we investigated the magnetic ordering of MnPS3, a two-dimensional antiferromagnetic material of Heisenberg-type, by Raman spectroscopy from bulk all the way down to bilayer. The phonon modes that involve the vibrations of Mn ions exhibit characteristic changes as the temperature gets lowered through the Néel temperature. In bulk MnPS3, the Raman peak at ~155 cm-1 becomes considerably broadened near the Néel temperature and upon further cooling is subsequently red-shifted. The measured peak positions and polarization dependences of the Raman spectra are in excellent agreement with our first-principles calculations. In few-layer MnPS3, the peak at ~155 cm-1 exhibits the characteristic red-shift at low temperatures down to the bilayer, indicating that the magnetic ordering is surprisingly stable at such a thin limit. Our work sheds light on the hitherto unexplored magnetic ordering in the Heisenberg-type antiferromagnetic systems in the atomic-layer limit.

cond-mat.mes-hall↗

arXiv2019

Bulk properties of van-der-Waals hard ferromagnet VI3

We present comprehensive measurements of the structural, magnetic and electronic properties of layered van-der-Waals ferromagnet VI$_3$ down to low temperatures. Despite belonging to a well studied family of transition metal trihalides, this material has received very little attention. We outline, from high-resolution powder x-ray diffraction measurements, a corrected room-temperature crystal structure to that previously proposed and uncover a structural transition at 79 K, also seen in the heat capacity. Magnetization measurements confirm VI$_3$ to be a hard ferromagnet (9.1 kOe coercive field at 2 K) with a high degree of anisotropy, and the pressure dependence of the magnetic properties provide evidence for the two-dimensional nature of the magnetic order. Optical and electrical transport measurements show this material to be an insulator with an optical band gap of 0.67 eV - the previous theoretical predictions of d-band metallicity then lead us to believe VI$_3$ to be a correlated Mott insulator. Our latest band structure calculations support this picture and show good agreement with the experimental data. We suggest VI$_3$ to host great potential in the thriving field of low-dimensional magnetism and functional materials, together with opportunities to study and make use of low-dimensional Mott physics.

cond-mat.str-el↗