arXiv subjects

Lun Jin

Publications and source records attributed to Lun Jin.

9 recordsLinked to original sources

arXiv2026

The Structure-tuning Magnetism in the Co(NbxTa1-x)2O6 Series

Low dimensional quantum materials have been extensively studied within the physics community, among which Co2+ is one of the most popular magnetic ions to be embedded into the structural motif. CoNb2O6 and CoTa2O6 both have adopted an effective spin-1/2 state, with the former attracting enduring interest while the latter being rarely investigated. This difference can be attributed to their distinct crystal structures, not only in crystal systems, but more important, how the CoO6 octahedra are connected. We successfully merge these two compounds together and map out the doping limits. We find out Ta and Nb dopants modify the properties of the parent compounds in subtle but different ways and construct a magnetic phase diagram of the Co(NbxTa1-x)2O6 (0 < x < 1) series. In addition, our results suggest that Ta-doping may pave a way to strengthen the lower-dimensional quantum phenomena in CoNb2O6 before its crystal structure starts to melt down.

cond-mat.mtrl-sci↗

arXiv2025

Recent Progress in Studies of Cobalt-based Quasi-1-dimensional Quantum Magnets

The interplay of crystal electric field, temperature, and spin-orbit coupling can yield a Kramers ion and thus an effective S = 1/2 ground state for Co2+ ions (3d7), which is often the case for low dimensional materials. This is because a highly anisotropic structural motif can force the spins to point either up or down, hence becoming a system where spins communicate via Ising interactions. Cobalt-based quasi-1-dimensional materials have been studied in this context since the latter half of the 20th century, but due to the development of modern characterization techniques and advances in sample preparation, the exotic physical phenomena that have generated the most interest have only emerged in the most recent three to four decades. This topical review mainly summarizes progress in cobalt-based quasi-1-dimensional quantum magnets, and comments on a few research directions of potential future interest.

cond-mat.mtrl-sci↗

arXiv2023

Is La3Ni2O6.5 a Bulk Superconducting Nickelate?

Superconducting states onsetting at moderately high temperatures have been observed in epitaxially-stabilized RENiO2-based thin films. However, recently it has also been reported that superconductivity at high temperatures is observed in bulk La3Ni2O7-{\delta} at high pressure, opening further possibilities for study. Here we report the reduction profile of La3Ni2O7 in a stream of 5% H2/Ar gas and the isolation of the metastable intermediate phase La3Ni2O6.45, which is based on Ni2+. Although this reduced phase does not superconduct at ambient or high pressures, it offers insights into the Ni-327 system and encourages the future study of nickelates as a function of oxygen content.

cond-mat.mtrl-sci↗

arXiv2023

Hidden Hydroxides in KOH-Grown BaNiO3 Crystals: A Potential Link to Their Catalytic Behavior

The hexagonal perovskite BaNiO3, prepared via non-ceramic approaches, is known to act as a good catalyst for the oxygen-evolution reaction (OER) in alkaline media. Here we report our observation that BaNiO3 synthesized via KOH flux growth and high O2 pressure ceramic synthesis have different magnetic properties. We show that this is because the KOH flux-grown crystals made in open-air are actually a hydroxide-containing form of BaNiO3 that can be dried upon annealing in O2 flow. This work not only unveils a previously unknown aspect of the BaNiO3 OER catalyst and offers some insights into the underlying mechanism, but also suggests that hydroxide ions may be present in other hexagonal perovskite oxides prepared in wet conditions.

cond-mat.mtrl-sci↗

arXiv2023

Stuffed Rare Earth Garnets

We report the synthesis and magnetic characterization of stuffed rare earth gallium garnets, RE3+xGa5-xO12 (RE=Lu, Yb, Er, Dy, Gd), for x up to 0.5. The excess rare earth ions partly fill the octahedral sites normally fully occupied by Ga3+, forming disordered pairs of corner-shared face-sharing magnetic tetrahedra. The Curie-Weiss constants and observed effective moments per rare earth are smaller than are seen for the unstuffed gallium garnets. No significant change in the field-dependent magnetization is observed but missing entropy is seen when integrating the low-temperature heat capacity to 0.5 K.

cond-mat.mtrl-sci↗

arXiv2023

Erbium-excess gallium garnets

A series of garnets of formula Er3+xGa5-xO12 is described, for which we report the crystal structures for both polycrystalline and single-crystal samples. The x limit in the garnet phase is between 0.5 and 0.6 under our conditions, with the Er fully occupying the normal garnet site plus half-occupying the octahedral site at x = 0.5 in place of the Ga normally present. Long-range antiferromagnetic order with spin ice-like frustration is suggested by the transition temperature (TN=0.8K) being much lower than the Curie-Weiss theta. The magnetic ordering temperature does not depend on the Er excess, but there is increasing residual entropy as the Er excess is increased, highlighting the potential for unusual magnetic behavior in this system.

cond-mat.mtrl-sci↗

arXiv2023

Electron Doping of a Double Perovskite Flat-band System

Electronic structure calculations indicate that the Sr2FeSbO6 double perovskite has a flat-band set just above the Fermi level that includes contributions from ordinary sub-bands with weak kinetic electron hopping plus a flat sub-band that can be attributed to the lattice geometry and orbital interference. To place the Fermi energy in that flat band, electron doped samples with formulas Sr2-xLaxFeSbO6 (0 < x < 0.3) were synthesized and their magnetism and ambient temperature crystal structures determined by high-resolution synchrotron X-ray powder diffraction. All materials appear to display an antiferromagnetic-like maximum in the magnetic susceptibility, but the dominant spin coupling evolves from antiferromagnetic to ferromagnetic on electron doping. Which of the three sub-bands or combinations is responsible for the behavior has not been determined.

cond-mat.mtrl-sci↗

arXiv2021

Magnetic-cations doped into a Double Perovskite Semiconductor

We report two solid solutions based on magnetic ion doping of the double perovskite oxide Sr2GaSbO6: Sr2Ga1-xCrxSbO6 (0.1 < x < 0.4) and Sr2Ga1-xFexSbO6 (0.1 < x < 0.4). All compositions crystallize in the same space group (I4/m) as their undoped parent phase Sr2GaSbO6, with the trivalent magnetic cations Cr3+ or Fe3+ partially substituting for non-magnetic Ga3+ in one of the B-cation sites. The Cr- and Fe-doped phases display dominant antiferromagnetic coupling among the dopant magnetic moments, and exhibit decreasing band gaps with increasing substitution level.

cond-mat.mtrl-sci↗

arXiv2021

Ferromagnetic Double Perovskite Semiconductors with Tunable Properties

We successfully dope the magnetically silent double perovskite semiconductor Sr2GaSbO6 to induce ferromagnetism and tune its band gap, with Ga3+ partially substituted by the magnetic trivalent cation Mn3+, in a rigid cation ordering with Sb5+. Our new ferromagnetic semiconducting Sr2Ga1-xMnxSbO6 double perovskite, which crystallizes in tetragonal symmetry (space group I4/m) and has tunable ferromagnetic ordering temperature and band gap, suggests that magnetic ion doping of double perovskites is a productive avenue towards obtaining materials for application in next-generation oxide-based spintronic devices.

cond-mat.mtrl-sci↗