Meng Wu

Bio: Meng Wu is an academic researcher from Shanghai University of Electric Power. The author has contributed to research in topics: Arrott plot & Phase transition. The author has an hindex of 1, co-authored 2 publications receiving 1 citations.

Martensitic Transformation and Barocaloric Effect in Co-V-Ga-Fe Paramagnetic Heusler Alloy

Abstract: In the present study, polycrystalline Co50V34Ga16−xFex (1≤x≤2) quaternary Heusler alloys were fabricated by the arc-melting method. It was found that they undergo a paramagnetic martensitic transformation (MT) from the L21-type cubic austenitic structure to the D022 tetragonal martensitic structure. With the increase of the Fe concentration, the MT shifts towards a higher temperature range, which is strongly related to the variation of the valence electron concentration. Moreover, it was also found that the MT exhibited by every alloy is sensitive to the applied hydrostatic pressure due to a relatively high difference in volume between the two phases. By using the quasi-direct method based on caloric measurements, the barocaloric effect (BCE) associated with the hydrostatic pressure-driven MT was estimated in the studied alloys. The results demonstrated that the sample with x=1.5 performs an optimal BCE among these three alloys.

Magnetic anomalies in a spin-chain compound, Sr3CuRhO6: Griffiths-phase-like behavior of magnetic susceptibility

Abstract: We report the results of ac and dc magnetic susceptibility (chi), heat-capacity (C), isothermal magnetization and isothermal remanent magnetization measurements on the compound, Sr3CuRhO6, crystallizing in a K4CdCl6-derived monoclinic structure. The magnetization data reveal distinct magnetic anomalies near 6 and 12 K with decreasing temperature (T). While the transition below (To=) 6K appears to be of a spin-glass-type as inferred from all the data, the one at 12 K is not typical of bulk ferromagnetism in contrast to an earlier proposal. In the range 6 to 12 K, the dc chi obeys the theoretically expected form for very low dc fields and the values of chi decrease gradually with the application of higher magnetic fields, mimicking the behavior Griffiths-phases.

Nontrivial Topological Features and Griffith’s-Phase Behavior in CrFeVGa Probed by Experiment and Theory

Abstract: We report a combined theoretical and experimental study of the topological semimetal CrFeVGa with an emphasis on the role of atomic disorder on the magnetoelectronic properties. CrFeVGa belongs to the quaternary Heusler alloy family and crystallizes in the cubic structure with B2 disorder. It is found that the disorder plays a crucial role in quenching the magnetization (net moment $\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\phantom{\rule{0.2em}{0ex}}{\ensuremath{\mu}}_{B}$ per formula unit) and other anomalies. Ac and dc magnetization data reveal the occurrence of Griffith's-phase-like behavior in the presence of small magnetic clusters with a weak antiferromagnetic or ferrimagnetic ordering. A nonsaturating, linear positive magnetoresistance is observed even at 70 kOe, in a wide temperature range, which is attributed to the quantum linear magnetoresistance arising due to the zero- or small-gap band structure. Hall measurements show some anomalous behavior (including an anomalous Hall conductivity ${\ensuremath{\sigma}}_{xy0}=270\phantom{\rule{0.2em}{0ex}}\mathrm{S}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ and an anomalous Hall angle of 0.07 at 2 K) with a significant contribution from the semimetallic bands. Hall data analysis also reveals the presence of some non-negligible topological Hall contribution, which is significant at low temperatures. Ab initio calculations confirm the topological Weyl behavior of CrFeVGa, which originates from a unique combination of broken time-reversal symmetry and noncentrosymmetry. The nontrivial band topology stems from the $p$ and $d$ states of vanadium, which overlap near the Fermi level. The presence of multi-Weyl points (24 pairs) near the Fermi level causes a large Berry curvature and hence reasonably high anomalous Hall conductivity. The coexistence of so many emerging features in a single material is rather rare and thus opens up new avenues for future topological and spintronics-based research.

Crystal structure and site preference, magnetic and elastic properties, and martensitic transformation of Ni- and Fe-doped Co2VGa alloys: A first-principles study

Abstract: Using the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, the crystal structure and site preference, magnetic and elastic properties, and martensitic transformation (MT) are systematically investigated with the three groups of Heusler alloys: (Co[Formula: see text]M[Formula: see text])VGa (M1[Formula: see text]), Co[Formula: see text](V[Formula: see text]M[Formula: see text])Ga (M2[Formula: see text]), and Co[Formula: see text]V(Ga[Formula: see text]M[Formula: see text]) (M3[Formula: see text], M = Ni and Fe, [Formula: see text]). It is shown that instead of the [Formula: see text] and [Formula: see text]A structures, the fcc one is energetically preferred in the cubic M3 x ([Formula: see text]) alloys. In [Formula: see text]-Ni2 x ([Formula: see text]) and fcc-Ni3 x ([Formula: see text]), Ni atoms even prefer the Ga and Co anti-sites, respectively, and the replaced atoms move to the sublattices of the deficient ones. Their total magnetic moment is dominated by the magnetic exchange interactions corresponding to the pairs of two Co atoms on the different sublattices in M = Ni and Fe1 x, Co and Fe in Fe2 x and Fe3 x ([Formula: see text]), and Fe and Fe atoms in Fe3 x ([Formula: see text]) alloys, respectively. These Ni1 x, Ni2 x, and Fe3 x with [Formula: see text] as well as Ni3 x with [Formula: see text] alloys are predicted having the MT behavior and also the better mechanical property relative to Co[Formula: see text]VGa. A lower shear modulus ([Formula: see text]) generally corresponds to a higher MT temperature, and these alloys, which can undergo the MT are further evaluated with [Formula: see text] GPa. Both considerable magnetocaloric and magnetovolume effects can be also expected during the MT of these Fe3 x alloys ([Formula: see text] and 0.6). In the remaining Fe1 x and Fe2 x alloys, the Fe doping disfavors the MT and also improves their brittleness. The structural preference of these cubic alloys and also their stability relative to the tetragonal martensite can be mainly attributed to the number of their minority density of states at the Fermi level: the smaller they are, the more stable their system tends to be.