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Giant Exfoliation Induced Magnetic Coercivity in Fe$_3$GaTe$_2$
Authors:
Lingrui Mei,
PeiYu Cai,
Sang-Eon Lee,
Yue Li,
Shyam Raj Karullithodi,
Vadym Kulichenko,
Charudatta Pathak,
Elton J. G. Santos,
Luis Balicas
Abstract:
Permanent magnets with strong anisotropy and high coercivity underpin modern information and energy technologies, yet rare-earth-free alternatives remain limited. Here, we show that thickness engineering via mechanical exfoliation induces hard magnetic behavior in the van der Waals ferromagnet Fe$_3$GaTe$_2$. Bulk crystals exhibit Curie temperatures above 350 K but negligible room-temperature coer…
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Permanent magnets with strong anisotropy and high coercivity underpin modern information and energy technologies, yet rare-earth-free alternatives remain limited. Here, we show that thickness engineering via mechanical exfoliation induces hard magnetic behavior in the van der Waals ferromagnet Fe$_3$GaTe$_2$. Bulk crystals exhibit Curie temperatures above 350 K but negligible room-temperature coercivity. When thinned below 100 nm, the coercive field is dramatically enhanced, reaching nearly 1 T at room temperature for in-plane fields which is comparable to values of conventional hard magnets. Micromagnetic analysis reveals a crossover in magnetization reversal from domain-mediated processes in bulk samples to quasi-coherent rotation in thin flakes, driven by increased effective anisotropy and suppressed domain formation. This thickness-dependent transition enables tuning of magnetic hardness without chemical modification. Combined with high saturation magnetization and robust room-temperature performance, Fe$_3$GaTe$_2$ emerges as a promising rare-earth-free material for spintronic applications. Its layered structure further allows integration into van der Waals heterostructures, where large in-plane coercivity can stabilize magnetic states against perturbations and interlayer coupling, offering potential for high-density nonvolatile memory and domain-wall-based devices.
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Submitted 30 July, 2026;
originally announced July 2026.
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Local Inversion Symmetry Breaking and Thermodynamic Evidence for Ferrimagnetism in Fe3GaTe2
Authors:
Sang-Eon Lee,
Yue Li,
Yeonkyu Lee,
W. Kice Brown,
PeiYu Cai,
Jinyoung Yun,
Chanyoung Lee,
Alex Moon,
Lingrui Mei,
Jaeyong Kim,
Yan Xin,
Julie A. Borchers,
Thomas W. Heitmann,
Matthias Frontzek,
William D. Ratcliff,
Gregory T. McCandless,
Julia Y. Chan,
Elton J. G. Santos,
Jeehoon Kim,
Charudatta M. Phatak,
Vadym Kulichenko,
Luis Balicas
Abstract:
The layered compound Fe3GaTe2 is attracting attention due to its high Curie temperature, low dimensionality, and the presence of topological spin textures above room temperature, making Fe$_3$GaTe$_2$ a good candidate for applications in spintronics. Here, we show, through transmission electron microscopy (TEM) techniques, that Fe$_3$GaTe$_2$ single crystals break local inversion symmetry while ma…
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The layered compound Fe3GaTe2 is attracting attention due to its high Curie temperature, low dimensionality, and the presence of topological spin textures above room temperature, making Fe$_3$GaTe$_2$ a good candidate for applications in spintronics. Here, we show, through transmission electron microscopy (TEM) techniques, that Fe$_3$GaTe$_2$ single crystals break local inversion symmetry while maintaining global inversion symmetry according to X-ray diffraction. Coupled to the observation of Néel skyrmions via Lorentz-TEM, our structural analysis provides a convincing explanation for their presence in centrosymmetric materials. Magnetization measurements as a function of the temperature displays a sharp first-order thermodynamic phase-transition leading to a reduction in the magnetic moment. This implies that the ground state of Fe$_3$GaTe$_2$ is globally ferrimagnetic and not a glassy magnetic state composed of ferrimagnetic, and ferromagnetic domains as previously claimed. Neutron diffraction studies indicate that the ferromagnetic to ferrimagnetic transition upon reducing the external magnetic field is associated with a change in the magnetic configuration/coupling between Fe1 and Fe2 moments. We observe a clear correlation between the hysteresis observed in both the skyrmion density and the magnetization of Fe$_3$GaTe$_2$. This indicates that its topological spin textures are affected by the development of ferrimagnetism upon cooling. Observation, via magnetic force microscopy, of magnetic bubbles at the magnetic phase boundary suggests skyrmions stabilized by the competition among magnetic phases and distinct exchange interactions. Our study provides an explanation for the observation of Néel skyrmions in centrosymmetric systems, while exposing a correlation between the distinct magnetic phases of Fe$_3$GaTe$_2$ and topological spin textures.
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Submitted 30 July, 2025;
originally announced July 2025.
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Who pumps spin current into nonmagnetic-metal (NM) layer in YIG/NM multilayers at ferromagnetic resonance?
Authors:
Yun Kang,
Hai Zhong,
Runrun Hao,
Shujun Hu,
Shishou Kang,
Guolei Liu,
Y. Zhang,
X. R. Wang,
Shishen Yan,
Yong Wu,
Shuyun Yu,
Guangbing Han,
Yong Jiang,
Liangmo Mei
Abstract:
Spin pumping in Yttrium-iron-garnet (YIG)/nonmagnetic-metal (NM) layer systems under ferromagnetic resonance (FMR) conditions is a popular method of generating spin current in the NM layer. A good understanding of the spin current source is essential in extracting spin Hall angle of the NM and in potential spintronics applications. It is widely believed that spin current is pumped from precessing…
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Spin pumping in Yttrium-iron-garnet (YIG)/nonmagnetic-metal (NM) layer systems under ferromagnetic resonance (FMR) conditions is a popular method of generating spin current in the NM layer. A good understanding of the spin current source is essential in extracting spin Hall angle of the NM and in potential spintronics applications. It is widely believed that spin current is pumped from precessing YIG magnetization into NM layer. Here, by combining microwave absorption and DC-voltage measurements on YIG/Pt and YIG/NM1/NM2 (NM1=Cu or Al, NM2=Pt or Ta), we unambiguously showed that spin current in NM came from the magnetized NM surface (in contact with YIG) due to the magnetic proximity effect (MPE), rather than the precessing YIG magnetization. This conclusion is reached through our unique detecting method where the FMR microwave absorption of the magnetized NM surface, hardly observed in the conventional FMR experiments, was greatly amplified when the electrical detection circuit was switched on.
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Submitted 24 April, 2016;
originally announced April 2016.
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Strong enhancement of critical current density in both low & high fields and flux pinning mechanism under hydrostatic pressure in optimally doped (Ba,K)Fe2As2 single crystals
Authors:
Babar Shabbir,
Xiaolin Wang,
Yanwei Ma,
Shixue Dou,
Shishen Yan,
Liangmo Mei
Abstract:
Strong pinning depends on the pinning force strength and number density of effective defects. Using hydrostatic pressure method, we demonstrate that hydrostatic pressure up to 1.2 GPa can significantly enhance flux pinning or Jc by a factor of up to 5 especially in both low and high fields in optimally doped Ba0.6K0.4Fe2As2 crystals. Our analysis on the flux pining mechanism indicate that both pin…
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Strong pinning depends on the pinning force strength and number density of effective defects. Using hydrostatic pressure method, we demonstrate that hydrostatic pressure up to 1.2 GPa can significantly enhance flux pinning or Jc by a factor of up to 5 especially in both low and high fields in optimally doped Ba0.6K0.4Fe2As2 crystals. Our analysis on the flux pining mechanism indicate that both pinning centre number density (Np) and pinning force (Fp) are greatly increased by the pressure and contribute to strong pinning.
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Submitted 17 November, 2015;
originally announced November 2015.
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Large rectification magnetoresistance in nonmagnetic Al/Ge/Al heterojunctions
Authors:
Kun Zhang,
Huan-huan Li,
Peter Grünberg,
Qiang Li,
Sheng-tao Ye,
Yu-feng Tian,
Shi-shen Yan,
Zhao-jun Lin,
Shi-shou Kang,
Yan-xue Chen,
Guo-lei Liu,
Liang-mo Mei
Abstract:
Magnetoresistance and rectification are two fundamental physical properties of heterojunctions and respectively have wide applications in spintronics devices. Being different from the well known various magnetoresistance effects, here we report a brand new large magnetoresistance that can be regarded as rectification magnetoresistance: the application of a pure small sinusoidal alternating-current…
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Magnetoresistance and rectification are two fundamental physical properties of heterojunctions and respectively have wide applications in spintronics devices. Being different from the well known various magnetoresistance effects, here we report a brand new large magnetoresistance that can be regarded as rectification magnetoresistance: the application of a pure small sinusoidal alternating-current to the nonmagnetic Al/Ge Schottky heterojunctions can generate a significant direct-current voltage, and this rectification voltage strongly varies with the external magnetic field. We find that the rectification magnetoresistance in Al/Ge Schottky heterojunctions is as large as 250% at room temperature, which is greatly enhanced as compared with the conventional magnetoresistance of 70%. The findings of rectification magnetoresistance open the way to the new nonmagnetic Ge-based spintronics devices of large rectification magnetoresistance at ambient temperature under the alternating-current due to the simultaneous implementation of the rectification and magnetoresistance in the same devices.
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Submitted 25 May, 2015;
originally announced May 2015.
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Anomalous Hall Effect in Variable Range Hopping Regime: Unusual Scaling Law and Sign Reversal with Temperature
Authors:
R. M. Qiao,
S. S. Yan,
T. S. Xu,
M. W. Zhao,
Y. X. Chen,
G. L. Liu,
W. L. Yang,
R. K. Zheng,
L. M. Mei
Abstract:
Anomalous Hall effect (AHE) is important for understanding the topological properties of electronic states, and provides insight into the spin-polarized carriers of magnetic materials. AHE has been extensively studied in metallic, but not variable-range-hopping (VRH), regime. Here we report the experiments of both anomalous and ordinary Hall effect (OHE) in Mott and Efros VRH regimes. We found unu…
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Anomalous Hall effect (AHE) is important for understanding the topological properties of electronic states, and provides insight into the spin-polarized carriers of magnetic materials. AHE has been extensively studied in metallic, but not variable-range-hopping (VRH), regime. Here we report the experiments of both anomalous and ordinary Hall effect (OHE) in Mott and Efros VRH regimes. We found unusual scaling law of the AHE coefficient $Rah=aRxx^b$ with b>2, contrasting the OHE coefficient $Roh=cRxx^d$ with d<1. More strikingly, the sign of AHE coefficient changes with temperature with specific electron densities.
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Submitted 22 June, 2014;
originally announced June 2014.
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Thermoelectric properties of Sr0.61Ba0.39Nb2O6-δ ceramics annealed in different oxygen-reduction conditions
Authors:
Y. Li,
J. Liu,
C. L. Wang,
W. B. Su,
Y. H. Zhu,
J. C. Li,
L. M. Mei
Abstract:
The thermoelectric properties of Sr0.61Ba0.39Nb2O6 ceramics, reduced in different conditions, were investigated in the temperature region from 323 K to 1073 K. The electrical transport behaviors of the samples are dominated by the thermal-activated polaron hopping, the Fermi glass behavior, and the Anderson localized behavior from low temperatures to high temperatures, respectively. The lattice th…
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The thermoelectric properties of Sr0.61Ba0.39Nb2O6 ceramics, reduced in different conditions, were investigated in the temperature region from 323 K to 1073 K. The electrical transport behaviors of the samples are dominated by the thermal-activated polaron hopping, the Fermi glass behavior, and the Anderson localized behavior from low temperatures to high temperatures, respectively. The lattice thermal conductivity presents a plateau at high temperatures, indicating a glass-like thermal conduction behavior. Both the thermoelectric power factor and the thermal conductivity increase with the increasing degree of oxygen-reduction. Taking these two factors into account, the oxygen-reduction can still contribute to promoting the thermoelectric figure of merit. The highest ZT value (~0.19 at 1073 K) is obtained in the heaviest oxygen reduced sample.
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Submitted 1 April, 2014;
originally announced April 2014.
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Determining Seebeck coefficient of heavily doped La:SrTiO3 from density functional calculations
Authors:
Rui-zhi Zhang,
Chun-lei Wang,
Ji-chao Li,
Jia-liang Zhang,
Ming-lei Zhao,
Jian Liu,
Peng Zheng,
Yan-fei Zhang,
Liang-mo Mei
Abstract:
A new approach is developed to calculate temperature dependent Seebeck coefficient of heavily doped systems by using Boltzmann transport theory and electron density of states (DOS) obtained from density functional calculations. This approach is applied to heavily doped La:STO with DOS from tetrahedral method and Fermi energy using Fermi integrals. The calculated Seebeck coefficient agrees with t…
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A new approach is developed to calculate temperature dependent Seebeck coefficient of heavily doped systems by using Boltzmann transport theory and electron density of states (DOS) obtained from density functional calculations. This approach is applied to heavily doped La:STO with DOS from tetrahedral method and Fermi energy using Fermi integrals. The calculated Seebeck coefficient agrees with the experimental data nearly quantitatively, which proved the accuracy of this approach. The influence of the Fermi energy and asymmetry of DOS on the Seebeck coefficient is analyzed.
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Submitted 4 April, 2012; v1 submitted 4 September, 2008;
originally announced September 2008.
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Bias-induced insulator-metal transition in organic electronics
Authors:
J. H. Wei,
Yijing Yan,
S. J. Xie,
L. M. Mei
Abstract:
We investigate the bias-induced insulator-metal transition in organic electronics devices, on the basis of the Su-Schrieffer-Heeger model combined with the non-equilibrium Green's function formalism. The insulator-metal transition is explained with the energy levels crossover that eliminates the Peierls phase and delocalizes the electron states near the threshold voltage. This may account for th…
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We investigate the bias-induced insulator-metal transition in organic electronics devices, on the basis of the Su-Schrieffer-Heeger model combined with the non-equilibrium Green's function formalism. The insulator-metal transition is explained with the energy levels crossover that eliminates the Peierls phase and delocalizes the electron states near the threshold voltage. This may account for the experimental observations on the devices that exhibit intrinsic bistable conductance switching with large on-off ratio.
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Submitted 10 July, 2007; v1 submitted 1 September, 2006;
originally announced September 2006.
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Charge-transfer polaron induced negative differential resistance and giant magnetoresistance in organic spintronics: A Su-Schrieffer-Heeger model study
Authors:
J. H. Wei,
S. J. Xie,
L. M. Mei,
J. Berakdar,
YiJing Yan
Abstract:
Combining the Su-Schrieffer-Heeger model and the non-equilibrium Green's function formalism, we investigate the negative differential resistance effect in organic spintronics at low temperature and interprete it with a self-doping picture. A giant negative magnetoresistance exceeding 300% is theoretically predicted as the results of the negative differential resistance effects.
Combining the Su-Schrieffer-Heeger model and the non-equilibrium Green's function formalism, we investigate the negative differential resistance effect in organic spintronics at low temperature and interprete it with a self-doping picture. A giant negative magnetoresistance exceeding 300% is theoretically predicted as the results of the negative differential resistance effects.
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Submitted 29 September, 2005; v1 submitted 29 September, 2005;
originally announced September 2005.
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Conductance switching, hysteresis, and magnetoresistance in organic semiconductors
Authors:
J. H. Wei,
S. J. Xie,
L. M. Mei,
YiJing Yan
Abstract:
The controllability of charge transport through an organic molecular spin-valve system is theoretically investigated on the basis of a Su-Schrieffer-Heeger model combined with the non-equilibrium Green's function formalism. We show how the formation of polaron in the organic sub-structure leads to a hysteretic conductance switching, via sweeping either the bias voltage or the electrochemical pot…
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The controllability of charge transport through an organic molecular spin-valve system is theoretically investigated on the basis of a Su-Schrieffer-Heeger model combined with the non-equilibrium Green's function formalism. We show how the formation of polaron in the organic sub-structure leads to a hysteretic conductance switching, via sweeping either the bias voltage or the electrochemical potential. We further obtain an exponential dependence of the magnetoresistance as a function of the applied bias voltage. The implications of calculated results in relation to experiments and device applications are addressed and commented.
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Submitted 20 August, 2006; v1 submitted 18 August, 2005;
originally announced August 2005.