Large Magnetoresistance Effect Research Articles

Unconventional room-temperature negative magnetoresistance effect in Au/n-Ge:Sb/Au devices

Non-magnetic semiconductor materials and their devices have attracted wide attention since they are usually prone to exhibit large positive magnetoresistance (MR) effect in a low static magnetic field environment at room temperature. However, how to obtain a large room-temperature negative MR effect in them remains to be studied. In this paper, by designing an Au/n-Ge:Sb/Au device with metal electrodes located on identical side, we observe an obvious room-temperature negative MR effect in a specific 50 T pulsed high magnetic field direction environment, but not in a static low magnetic field environment. Through the analysis of the experimental measurement of the Hall effect results and bipolar transport theory, we propose that this unconventional negative MR effect is mainly related to the charge accumulation on the surface of the device under the modulation of the stronger Lorentz force provided by the pulsed high magnetic field. This theoretical analytical model is further confirmed by regulating the geometry size of the device. Our work sheds light on the development of novel magnetic sensing, magnetic logic and other devices based on non-magnetic semiconductors operating in pulsed high magnetic field environment.

High-Mobility Topological Semimetals as Novel Materials for Huge Magnetoresistance Effect and New Type of Quantum Hall Effect.

The quantitative description of electrical and magnetotransport properties of solid-state materials has been a remarkable challenge in materials science over recent decades. Recently, the discovery of a novel class of materials-the topological semimetals-has led to a growing interest in the full understanding of their magnetotransport properties. In this review, the strong interplay among topology, band structure, and carrier mobility in recently discovered high carrier mobility topological semimetals is discussed and their effect on their magnetotransport properties is outlined. Their large magnetoresistance effect, especially in the Hall transverse configuration, and a new version of a three-dimensional quantum Hall effect observed in high-mobility Weyl and Dirac semimetals are reviewed. The possibility of designing novel quantum sensors and devices based on solid-state semimetals is also examined.

Nontrivial spin textures induced remarkable topological Hall effect and extraordinary magnetoresistance in kagome magnet TmMn6Sn6

Kagome magnets RMn6Sn6 (R = lanthanides) manifest novel topological phases and field-induced transitions, owing to the interplay between strong correlations and geometrical frustration among the corner-sharing-triangle intralayers. Here we report the magnetometry and magnetoelectric transport properties of TmMn6Sn6 single crystal, which coexists with Tm and Mn magnetic sublattices. We reveal that this compound displays multiple magnetic structures with the increase of in-plane magnetic field. The combination of non-collinear magnetic structure and real-space Berry curvature leads to a remarkable topological Hall effect over an extensive temperature range. The in-plane magnetic transition is accompanied by a large magnetoresistance effect of -32 ∼ -17% from 10 K to 300 K at 7 T, and the magnetoresistance manifests two peaks with increasing the in-plane field. These observations suggest a robust Mn - Tm magnetic coupling, which provides a nontrivial ferrimagnetic network for the further investigation of new emergent topological magnetic structures.

Giant intrinsic magnetoresistance in spin-filtered tunnel junctions with ferrimagnetic electrode

In recent years, magnetic tunnel junctions (MTJs) have attracted strong research interest due to their potential use in nonvolatile memory technologies, such as magnetoresistive random access memory and magnetic logic applications. Half-metallic materials have been proposed as ideal electrode materials for MTJs to achieve large tunnel magnetoresistance (TMR) effects. Here, we design and investigate a spin-filter MTJ (sf-MTJ) consisting of a ferrimagnetic inverse Heusler alloy, ${\mathrm{Mn}}_{2}\mathrm{CoSi}$ as the electrode and CaS as the insulating tunnel barrier using ab initio quantum transport calculations. Our results demonstrate a high zero-bias voltage TMR ratio that initially oscillated before decreasing as the bias voltage increased. Despite the oscillatory TMR under bias voltage, the spin injection remains high and stable, highlighting the potential of sf-MTJs formed by ${\mathrm{Mn}}_{2}\mathrm{CoSi}$ electrodes for practical applications.

Large magnetoresistance and temperature-driven spin filter effect in spin valve based on half Heusler alloy.

High spin-injection-efficiency (SIE) and thermal spin-filter-effect (SFE) from a magnetic material to a barrier material are crucial to the high performance of a spintronic device and a spin caloritronic device, respectively. By performing a nonequilibrium Green's function combined with first-principles calculations, we study the voltage-driven and temperature-driven spin transport properties of a half Heusler alloy RuCrAs based spin valve with different atom-terminated interfaces. The spin valve with a CrAs-top (or Ru-top) interface structure has an ultrahigh equilibrium magnetoresistance (MR) ratio of ∼1.56 × 109% (or ∼5.14 × 108%), ∼100% SIE, a large MR ratio, and high spin current intensity under bias voltage, suggesting that it has a great potential application in spintronic devices. The spin valve with the CrAs-top (or CrAs-bri) interface structure has a perfect SFE due to its very high spin polarization of temperature-driven currents, and it is useful in spin caloritronic devices.

Synthesis of Two-Dimensional MoO2 Nanoplates with Large Linear Magnetoresistance and Nonlinear Hall Effect.

Two-dimensional (2D) materials with large linear magnetoresistance (LMR) are very interesting owing to their potential application in magnetic storage or sensor devices. Here, we report the synthesis of 2D MoO2 nanoplates grown by a chemical vapor deposition (CVD) method and observe large LMR and nonlinear Hall behavior in MoO2 nanoplates. As-obtained MoO2 nanoplates exhibit rhombic shapes and high crystallinity. Electrical studies indicate that MoO2 nanoplates feature a metallic nature with an excellent conductivity of up to 3.7 × 107 S m-1 at 2.5 K. MoO2 nanoplates display a large LMR of up to 455% at 3 K and -9 T. A thickness-dependent LMR analysis suggests that LMR values increase upon increasing the thickness of nanoplates. Besides, nonlinearity has been found in the magnetic-field-dependent Hall resistance, which decreases with increasing temperatures. Our studies highlight that MoO2 nanoplates are promising materials for fundamental studies and potential applications in magnetic storage devices.

Ferromagnetic exchange field-controlled band dispersions of non-Dirac electrons

Using model analysis and first-principles calculations, we demonstrate that intrinsic ferromagnetic field of materials can effectively modulate the non-Dirac band dispersions. The four-bands k·p model illustrates that rotating magnetization from in-plane to out-of-plane lifts the degeneracy of band dispersions at Γ point, and spin components of lower or upper two bands tend to become identical as the enhancement of exchange field, which results in non-trivial topology. Moreover, we exemplify these phenomena in stanene-based systems, namely stanene/hematene heterostructure and half-hydrogen-passivated stanene, respectively. Some interesting spin-dependent transport behavior, such as large magnetoresistance and quantum anomalous hall effect, are achieved. These findings enrich the physics of non-Dirac electrons and provide promising routes for realizing effective manipulation of band dispersions via spin freedom.

Large magnetocaloric and magnetoresistance effects during martensitic transformation in Heusler-type Ni44Co6Mn37In13 alloy

NiMn-based Heusler alloys are promising materials in the multi-functional applications due to their ample magneto-responsive effects across martensitic transformation, such as magnetocaloric effect, magnetostriction and magnetoresistance. In this work, the evolution of microstructure, large magnetocaloric and magnetoresistance effects during martensitic transformation are systematically studied in a Ni44Co6Mn37In13 alloy. Magnetic and caloric measurements verify that the martensite in weak magnetic state would gradually transform to be ferromagnetic austenite upon heating. The temperature dependence of microstructure observed in an in-situ optical microscopy unambiguously verify the ‘kinetic arrest’ of martensitic transformation. Most importantly, due to the high sensitivity of transformation to the magnetic field, large magnetocaloric and magnetoresistance effects near room temperature are obtained, including magnetic entropy changes of 8.4 Jkg-1K−1, effective refrigerant capacity of 181 Jkg−1 and magnetoresistance change of 75 % under the field change of Δμ0H = 0–5 T, making the studied sample promising for room temperature magnetic refrigeration and magnetic storage.

Dispenser Printed Bismuth‐Based Magnetic Field Sensors with Non‐Saturating Large Magnetoresistance for Touchless Interactive Surfaces (Adv. Mater. Technol. 10/2022)

Printed Magnetic Field Sensors In article number 2200227, Mykola Vinnichenk, Denys Makarov, and co-workers present dispenser printing of magnetic field sensors based on bismuth powder. Benefiting from the non-saturating large magnetoresistance effect, this technology enables scalable large-area printing of sensors with broad detection range on flexible and rigid substrates. Touchless interactive surfaces based on dispenser-printed magnetically sensitive devices are demonstrated.

The transport properties and large magnetoresistance effect in Pr0.7Sr0.3MnO3 film on SrTiO3

The transport properties and large magnetoresistance effect in Pr0.7Sr0.3MnO3 film on SrTiO3

Superconductivity and weak anti-localization in nodal-line semimetal SnTaS2

Topological semimetals with superconducting properties provide an emergent platform to explore the properties of topological superconductors. We report magnetization, and magneto-transport measurements on high quality single crystals of transition metal dichalcogenide SnTaS2. It is a nodal line semimetal with superconducting transition below T c = 2.9 K. Moderate anisotropy (γ = 3.1) is observed in upper critical fields along H//c and H//ab plane. In the normal state we observe large magneto-resistance and weak anti-localization effect that provide unambiguous confirmation of topological features in SnTaS2. Therefore, genuine topological characteristics can be studied in this material, particularly with regard to microscopic origin of order parameter symmetry.

Giant Negative Magnetoresistance beyond Chiral Anomaly in Topological Material YCuAs2.

The large negative magnetoresistance (MR) effect, which usually emerges in various magnetic systems, is a technologically important property for spintronics. Recently, the so-called "chiral anomaly" in topological semimetals offers an alternative to generate a considerable negative MR effect without utilizing magnetism. However, it requires that the applied magnetic field must be strictly along the electric current direction, which sets a strong limit for practical applications. Here, a giant negative MR effect is discovered with a value of up to -40% in 9 T at 2 K in the nonmagnetic Dirac material YCuAs2 , which is not restricted to the specific configuration for applied magnetic fields. Based on magnetic susceptibility and NMR measurements, the giant negative MR effect is tightly connected with the unexpected spin-dependent scattering from vacancy-induced local moments, which is also beyond the classical Kondo effect. The present work not only offers an alternative route for spintronics based on nonmagnetic topological materials, but also helps to further understand the negative MR effect in topological materials.

Dispenser Printed Bismuth‐Based Magnetic Field Sensors with Non‐Saturating Large Magnetoresistance for Touchless Interactive Surfaces

AbstractPrinted magnetic field sensors enable a new generation of human‐machine interfaces and contactless switches for resource‐efficient printed interactive electronics. As printed magnetoresistors rely on scarce or hard to manufacture magnetosensitive powders, their scalability and demonstration of printing with industry‐grade technologies are the key material science challenges. Here, the authors report dispenser printing of a commodity scale nonmagnetic bismuth‐based paste processed by large area laser sintering to obtain printed magnetoresistive sensors. The sensors are printed on different substrates including ceramics, paper, and polymer foils. It is validated experimentally that the peculiar quantum large orbital magnetoresistive effect remains effective in printed bismuth sensors, allowing their operation in high magnetic fields. The sensors reveal up to 146% resistance change at 5 T at room temperature with a maximum resolution of 2.8 μT. If printed on flexible foils, these sensors show resilience to bending deformation for more than 2000 bending cycles and withstand even thermal forming, as relevant for smart wearables and in‐mold electronics. The freedom in the substrate choice and sensor design enabled by dispenser printing allows to implement the proposed sensor technology for different applications focused on touchless interactive platforms, such as advertisement materials, interactive wallpapers, and printed security panels.

Planar Hall effect and large anisotropic magnetoresistance in a topological superconductor candidate Cu0.05PdTe2

We report the observation of a large anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) in a topological superconducting candidate Cu0.05PdTe2. The AMR and PHE data in Cu0.05PdTe2 can be well explained by the semiclassical theory, confirming that the magneto-transport behaviors of the Cu0.05PdTe2 superconductor are related to its topological nature. The AMR ratio in Cu0.05PdTe2 is one order of magnitude larger than those in traditional ferromagnetic metals. The present results suggest that Cu0.05PdTe2 is a promising material in future magnetoresistive devices with low power consumption.

Enhancing the interfacial perpendicular magnetic anisotropy and tunnel magnetoresistance by inserting an ultrathin LiF layer at an Fe/MgO interface

Perpendicular magnetic anisotropy (PMA) is becoming increasingly important in spintronics research, especially for high-density magnetoresistive random access memories (MRAMs). The PMA induced at an Fe/MgO interface is widely used in magnetic tunnel junctions. Here, we propose inserting an ultrathin LiF layer at the interface in an epitaxial Fe/MgO junction. With a 0.3 nm-thick LiF layer, a large intrinsic interface PMA energy, Ki,0, of 2.8 mJ/m2 was achieved. We also found that the LiF/MgO bilayer tunneling barrier exhibited a large tunnel magnetoresistance (TMR) effect, suggesting that a coherent spin-dependent tunneling process was maintained in the ultrathin LiF layer. Atomic-scale interface engineering using fluoride can further improve the PMA and TMR properties of spintronic devices.

A large negative magnetoresistance effect in semiconducting crystals composed of an octahedrally ligated phthalocyanine complex with high-spin manganese(iii).

A design for an octahedrally ligated phthalocyanine complex with high-spin manganese(iii) (S = 2) and MnIII(Pc)Cl2 (Pc = phthalocyanine) is presented. The presence of high-spin state MnIII in the fabricated Ph4P[MnIII(Pc)Cl2]2 (Ph4P = tetraphenylphosphonium) semiconducting molecular crystal is indicated by the Mn–Cl distance, which suggests an electronic configuration of (dyz, dzx)2(dxy)1(dz2)1. This was confirmed by the Curie constant (C = 5.69 emu K mol−1), which was found to be significantly larger than that of the isostructural Ph4P[MnIII(Pc)(CN)2]2, where MnIII adopts a low-spin state (S = 1). The magnetoresistance (MR) effects of Ph4P[MnIII(Pc)Cl2]2 at 26.5 K under 9 T static magnetic fields perpendicular and parallel to the c-axis were determined to be −30% and −20%, respectively, which are significantly larger values than those of Ph4P[MnIII(Pc)(CN)2]2. Furthermore, the negative MR effect is comparable to that of Ph4P[FeIII(Pc)(CN)2]2 (S = 1/2), which exhibits the largest negative MR effect reported for [MIII(Mc)L2]-based systems (Mc = macrocyclic ligand, L = axial ligand). This suggests that the spin state of the metal ion is the key to tuning the MR effect.

Room-temperature magnetoresistance in Ni78Fe22/C8-BTBT/Ni78Fe22 nanojunctions fabricated from magnetic thin-film edges using a novel technique.

Molecular spintronic devices are gaining popularity because the organic semiconductors with long spin relaxation times are expected to have long spin diffusion lengths. A typical molecular spintronic device consists of organic molecules sandwiched between two magnetic layers, which exhibits magnetoresistance (MR) effect. Nanosized devices are also expected to have a high spin polarization, leading to a large MR effect owing to effective orbital hybridization. However, most studies on nanosized molecular spintronic devices have investigated the MR effect at low temperatures because of the difficulty in observing the MR effect at room temperature. Here we focus on high-mobility molecules expected to show long spin diffusion lengths, which lead to the observation of the MR effect in nanoscale junctions at room temperature. In this study, we fabricate magnetic nanojunctions consisting of high-mobility molecules, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), sandwiched between two Ni78Fe22 thin films with crossed edges. Transmission electron microscopy (TEM) images reveal that C8-BTBT molecular layers with smooth and clear interfaces can be deposited on the Ni78Fe22 thin-film edges. Consequently, we observe a clear positive MR effect, that is, R P < R AP, where R P and R AP are the resistances in the parallel (P) and antiparallel (AP) configurations, respectively, of two magnetic electrodes in the Ni78Fe22/C8-BTBT/Ni78Fe22 nanojunctions at room temperature. The obtained results indicate that the spin signal through the C8-BTBT molecules can be successfully observed. The study presented herein provides a novel nanofabrication technique and opens up new opportunities for research in high-mobility molecular nano-spintronics.

Effect of Fe substitution on temperature coefficient of resistance and magnetoresistance of La0.67Ca0.33MnO3 polycrystalline ceramics

La0.67Ca0.33MnO3 perovskite manganate exhibits high temperature coefficient of resistance (TCR) and large magnetoresistance (MR) effect, these enable novel multifunctionalities. Mn site substitution can change magnetic order of the manganates, thereby tailoring both electrical and magnetic transport. Herein, La0.67Ca0.33Mn1-xFexO3(0 ≤ x ≤ 0.06) polycrystalline ceramics were prepared by sol-gel route. The effect of Fe substitution on TCR and MR of La0.67Ca0.33MnO3 was studied. Fe replacing Mn ions, would weaken double exchange, and significantly reduced Curie temperature and ferromagnetism. Additionally, Fe doping promoted the development of grain. TCR increased first with Fe content x and then decreased, and reached 45.2%·K-1 at x = 0.01, which is the highest value reported. Notably, with Fe doping, MR gradually increased and reached 81.1% (1 T) at x = 0.06. Fe doping can significantly enhance TCR and MR, which generates promising potential in (uncooled) thermistor/infrared detecting and magnetic sensors.

Magnetic properties and magnetoresistance effect of SnFe2O4 spinel nanoparticles: Experimental, ab initio and Monte Carlo simulation

In this contribution, SnFe2O4 nanoparticles were prepared by the solvothermal method, the structural properties were performed using X-Ray Diffraction (DRX) to prove the success of tin ferrite formation and to determine de crystals parameters. The size and morphological study were build using Scanning Electron Microscopy (SEM) and Transmission Electron microscopy (TEM), the results showed that the size of particles is uniform with a range of particles (5–7 nm). The magnetic properties were carried out using the SQUID device, the SnFe2O4 nanoparticles have a magnetic transition at 750 K. In addition, the hysteresis loops at low temperature displayed Ms and Mr equals to 23 emu/g and 6 emu/g, respectively. The magnetoresistance properties were investigated, the SnFe2O4 nanoparticles present a large magnetoresistance effect (80%). The experimental results are supplemented by model calculations utilizing density functional theory and Monte-Carlo simulations.

Magnetic-field-induced avalanches in magnetization and magnetoresistance of La0.9Ce0.1Fe12B6 compound

Competition between paramagnetic (PM), antiferromagnetic (AFM) and ferromagnetic (FM) phases in La0.9Ce0.1Fe12B6 itinerant-electron metamagnetic system is studied by a combination of magnetic, electrical resistivity and magnetoresistance measurements. La0.9Ce0.1Fe12B6 is an antiferromagnet below the Néel temperature (35 K) and presents two consecutive magnetic transitions AFM–FM and FM–PM during warming under certain applied magnetic field values. We further demonstrate that both AFM and PM phases may be converted into the FM phase irreversibly and reversibly via a first-order metamagnetic transition accompanied by a large magnetic field hysteresis. At very low temperatures, the magnetic-field-driven AFM–FM metamagnetic transformation is discontinuous and proceeds by multiple abrupt steps in magnetization and magnetoresistance. In addition, an extraordinarily large negative magnetoresistance (MR) effect of −77% is observed. The consistency found in the magnetotransport and magnetization data suggests strong correlations between charge and spin degrees of freedom in La0.9Ce0.1Fe12B6 system.