arXiv subjects

Ankush Saxena

Publications and source records attributed to Ankush Saxena.

6 recordsLinked to original sources

arXiv2026

Ferromagnetic Spin Glass State and Anomalous Hall Effect in Topological Semimetal Candidate Mn2Sb2Te5

Materials that intrinsically possess both magnetism and topological states represent a key frontier of quantum materials research. Recently, Mn2(Bi/Sb)2Te5 has emerged as a promising candidate for hosting topological surface states coupled with intrinsic magnetic order, making it a potential magnetic Weyl semimetal. In this study, we investigate the magnetic and transport properties of Mn2Sb2Te5 single crystals. The magnetization measurements reveal a spin glass state with field-induced ferromagnetism. Although heat capacity measurement indicates the absence of long-range order, the intrinsic magnetization in Mn2Sb2Te5 significantly affects its electrical properties, as demonstrated by the anomalous Hall effect. This work provides valuable insights into the magnetism and the electronic properties of Mn2Sb2Te5, establishing Mn2(Bi/Sb)2Te5 system as a compelling platform for exploring the interplay between magnetism and non-trivial band topology, enabling emergent quantum phases and novel transport responses not accessible in non-magnetic systems.

cond-mat.mtrl-sci↗

arXiv2023

Growth and characterization of the magnetic topological insulator candidate Mn$_2$Sb$_2$Te$_5$

We report a new member of topological insulator (TI) family i.e., Mn$_2$Sb$_2$Te$_5$, which belongs to MnSb$_2$Te$_4$ family and is a sister compound of Mn$_2$Bi$_2$Te$_5$. An antiferromagnetic layer of (MnTe)$_2$ has been inserted between quintuple layers of Sb$_2$Te$_3$. The crystal structure and chemical composition of as grown Mn$_2$Sb$_2$Te$_5$ crystal is experimentally visualized by single crystal XRD (SCXRD) and field emission scanning electron microscopy (FESEM). The valence states of individual constituents i.e., Mn, Sb and Te are ascertained through X ray photo electron spectroscopy (XPS). Different vibrational modes of Mn$_2$Sb$_2$Te$_5$ are elucidated through Raman spectroscopy. Temperature-dependent resistivity of Mn$_2$Sb$_2$Te$_5$ resulted in metallic behaviour of the same with an up-turn at below around 20K. Further, the magneto-transport R(T) vs H of the same exhibited negative magneto-resistance (MR) at low temperatures below 20K and small positive at higher temperatures. The low Temperature -ve MR starts decreasing at higher fields. The magnetic moment as a function of temperature at 100Oe and 1kOe showed AFM like down turn cusps at around 20K and 10K. The isothermal magnetization (MH) showed AFM like loops with some embedded FM/PM domains at 5K and purely paramagnetic (PM) like at 100K. The studied Mn$_2$Sb$_2$Te$_5$ clearly exhibited the characteristics of a magnetic TI (MTI).

cond-mat.mtrl-sci↗

arXiv2022

Detailed structural and topological analysis of SnBi2Te4 single crystal

We report herein the successful synthesis of the topological material SnBi2Te4 in single-crystal form. Phase purity and unidirectional growth are evident from X-ray diffraction (XRD) patterns acquired from a powdered sample and a crystal flake. The crystalline morphology has also been visualized by acquiring a field-emission scanning electron microscope (FESEM) image. The crystal has been thoroughly characterized by means of Raman spectroscopy and X ray photoelectron spectroscopy (XPS) measurements. The topological properties of SnBi2Te4 have been probed through magneto-transport measurements. SnBi2Te4 has been found to exhibit a small but non-saturating magneto-resistance (MR) up to 12 T. The low-field magnetoconductivity (MC) of SnBi2Te4 at 2 K can be well explained through the Hikami Larkin Nagaoka (HLN) formalism, which confirms the presence of a weak anti-localization (WAL) effect in its crystal. Moreover, the non-trivial topological character has been evidenced through first-principles calculations using density functional theory (DFT), with and without spin-orbit coupling (SOC) protocols. A significant change in the bulk electronic band structure is observed upon the inclusion of SOC parameters, signifying the topological properties of SnBi2Te4. Its topological non-trivial character has also been verified through the calculation of Z2 invariants and the surface states spectrum in the (111) plane.

cond-mat.mtrl-sci↗

arXiv2021

Structural and WAL analysis of Topological single-crystal SnSb2Te4

Here, we report successful single crystal growth of SnSb2Te4 using the self-flux method. Unidirectional crystal growth is confirmed through X Ray Diffraction (XRD) pattern taken on mechanically cleaved crystal flake while the rietveld refined Powder XRD (PXRD) pattern confirms the phase purity of the grown crystal. Scanning Electron Microscopy (SEM) image and Energy Dispersive X-Ray analysis (EDAX) confirm crystalline morphology and exact stoichiometry of constituent elements. Vibrational Modes observed in Raman spectra also confirm the formation of the SnSb2Te4 phase. DC resistivity measurements confirm the metallic character of the grown crystal. Magneto-transport measurements up to 5T show a nonsaturating low magneto-resistance percentage. V type cusp and Hikami Larkin Nagaoka (HLN) fitting at lower field confirms the Weak Anti-localization (WAL) effect in SnSb2Te4. Density Functional Theory (DFT) calculations were showing topological non-trivial electronic band structure. It is the first-ever report on MR study and WAL analysis of SnSb2Te4 single crystal.

cond-mat.mtrl-sci↗

arXiv2020

Crystal Growth and characterization of possible New Magnetic Topological Insulators FeBi2Te4

Here we report successful single crystal growth of new possible magnetic topological insulator (MTI) FeBi2Te4 by self-flux method via vacuum encapsulation process. The detailed Rietveld analysis of Powder XRD data shows the as grown MTI crystal to be mainly dominated by FeBi2Te4 phase along with minority phases of Bi2Te3 and FeTe. Scanning electron microscope (SEM) image shows the morphology of as grown MTI single crystal to be of layered type laminar structure. Raman spectroscopy of the crystal exhibited three distinct phonon modes at 65, 110, and 132 cm-1 along with two split secondary modes at 90, and 144cm-1. The secondary split modes are result of FeTe intercalation in Bi2Te3 unit cell. Magneto-resistance measurement has been performed at different temperatures i.e. 200K, 20K and 2K in applied magnetic fields up to 12 Tesla, which showed very low MR in comparison to pure Bi2Te3 crystal. Temperature dependence of DC magnetization measurements show the FeBi2Te4 crystal to be mainly of ferromagnetic (FM) or ferri-magnetic nature above 295 K, albeit a secondary weak magnetic transition is seen at 54-46K as well. Detailed isothermal magnetization (MH) results showed that FM saturation moment at 295K is 0.00213emu/g, which is nearly invariant till 400 K. Summary, we had grown an MTI FeBi2Te4 single crystal, which may be a possible entrant for Quantum Anomalous Hall (QAH) effect at room temperature or above.

cond-mat.mtrl-sci↗

arXiv2019

Crystal Growth and basic transport and magnetic properties of MnBi2Te4

We report successful growth of magnetic topological insulator (MTI) MnBi2Te4. The heating schedule basically deals with growth of the crystal from melt at 900C and very slow cooling (1C/hr) to around 600C with 24 hours hold time, followed by cooling to room temperature. Our detailed, PXRD Reitveld analysis showed that the resultant crystal is dominated mainly by MnBi2Te4 and minor phases of Bi2Te3 and MnTe. The transport measurements showed a step like behavior at around 150K followed by cusp like structure in resistivity at around 25K (TP) due reported anti-ferromagnetic ordering of Mn. Both the resistivity transitions are seen clearly in dR/dT measurements at 150K and 20K respectively. The 25K transition of the compound is also seen in magnetic susceptibility. Low temperature (5K) magnetoresistance (MR) in applied field of up to 6 Tesla exhibited negative ve MR below 3 Tesla and +ve for higher fields. Also, seen are steps in MR below one Tesla. The studied MnBi2Te4 MTI crystal could be a possible candidate for Quantum Anomalous Hall (QAH) effect.

cond-mat.mtrl-sci↗