The thermal hysteresis of the electronic transport properties were studied for V2O3 thin films. The temporal evolution of the resistance shows the out-of-equilibrium nature of this hysteresis with a very slow relaxation. Partial cycles reveal not only a behavior consistent with phase coexistence, but also the presence of spinodal temperatures which are largely separated. The temperature spreading of phase coexistence is consistent with the bulk phase diagram in the pressure-temperature plane, confirming that the film is effectively under an effective pressure induced by the substrate.
利用纵向磁光克尔效应（MOKE）和感应磁通测量法，对Fe $_{73.5}$ Cu $_1$ Nb $_3$ Si $_13.5$ B $_9$三个系列的Finemet薄膜进行了一系列的动态磁滞回线测量。的MOKE动态磁滞回线显示出更显着的变化与频率比电感的，而这两种测量显示出类似的依赖于频率的平方根。我们在一个简单的畴壁脱钉模型的框架中分析这些结果，该模型解释了数据的一般行为。
Investigation of scaling properties of hysteresis in Finemet thin films
利用磁通测量装置研究了Finemet Fe $_{73.5}$ Cu $_1$ Nb $_3$ Si $_{18.5}$ B $_4$薄膜的磁滞回线行为。的滞后区域的标度律的存在下，研究作为所施加的场的振幅和频率的函数，考虑样品厚度从约20 nm到5 $μ$ m。我们没有观察到理论模型预测的任何缩放，而动态循环显示出对频率的对数依赖性。
Pt ultrathin films on ferromagnetic insulators have been widely studied for spintronics applications, and magnetic moments of interface Pt atoms were considered to be ferromagnetically ordered due to a magnetic proximity effect (MPE). An anomalous Hall effect (AHE) is usually used to examine an out-of-plane magnetic moments of the Pt layer. To tune ferromagnetic properties of an Pt ultrathin film, we fabricated electric double layer transistors on Pt thin films with thicknesses of 5.9 nm and 7.0 nm on a $\rm{CoFe_2O_4}$ (CFO) ferrimagnetic insulator. For the Pt (7.0 nm)/CFO sample, a hysteresi…
Mechanical strain can modify the structural and electronic properties of methylammonium lead iodide MAPbI3. The consequences of ferroelastic hysteresis, which involves the retention of structural memory upon cycles of deformation, in polycrystalline thin films of MAPbI3 are reported. Repeatedly bent films of MAPbI3 on flexible polyimide substrates were examined using Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) to quantitatively characterize the strain state, populations, and minimum sizes of twin domains. Approximate locations for the coercive stress and saturation on the ferroelast…
The metal-insulator transition (MIT) in vanadium dioxide (VO2) has the potential to lead to a number of disruptive technologies, including ultra-fast data storage, optical switches, and transistors which move beyond the limitations of silicon. For applications, VO2 films are deposited on crystalline substrates to prevent cracking observed in bulk VO2 crystals across the thermally driven MIT. Near the MIT, VO2 films exhibit nanoscale coexistence between metallic and insulating phases, which opens up further potential applications such as memristors, tunable capacitors, and optically engineered …
Highly ordered Bi2FeMnO6 epitaxial thin films have been successfully grown on SrTiO3 substrate. Both synchrotron X-ray reciprocal space mapping and high resolution transmission electron microscopy confirmed the alternative alignment of Fe and Mn along [111] direction of Bi2FeMnO6 films. Magnetic and ferroelectric properties of Bi2FeMnO6 films are characterized and analyzed. The room-temperature ferroelectricity is well kept in Bi2FeMnO6 film as expected. However, it is very interesting that Bi2FeMnO6 film exhibits a typical spin-glass behavior and very weak magnetism rather than a ferri/ferrom…
Ferroelectric interfaces are unique model objects for fundamental studies of polar surface properties such as versatile screening mechanisms of spontaneous polarization by free carriers and possible ion exchange with ambient media. The effect of ionic adsorption by electrically-open (i.e. non-electroded) ferroelectric surface on polarization reversal in the ferroelectric had been investigated experimentally and theoretically, however the effect influence on the temperature behaviour of polarization hysteresis remains unexplored. Also the comparative theoretical analysis of the ferroelectric hy…
We have performed magnetotransport measurements in CeTe$_{3}$ thin films down to $0.2~{\rm K}$. It is known that CeTe$_{3}$ has two magnetic transitions at $T_{\rm N1} \approx 3~{\rm K}$ and $T_{\rm N2} \approx 1~{\rm K}$. A clear Shubnikov-de-Haas (SdH) oscillation was observed at $4~{\rm K}$, demonstrating the strong two-dimensional nature in this material. Below $T_{\rm N2}$, the SdH oscillation has two frequencies, indicating that the Fermi surface could be slightly modulated due to the second magnetic transition. We also observed a magnetic hysteresis in the SdH oscillation below $T_{\rm …
Space charge dynamics in solid electrolytes with steric effect and Vegard stresses: resistive switching and ferroelectric-like hysteresis of electromechanical response
A novel vertical hysteresis loop shift is observed for a bilayer thin film of Ni80Fe20/SrRuO3 (1:2 thickness ratio) on SrTiO3 substrate, after field cooled through the Curie temperature ~125 K of SrRuO3, whereas no shift is found for zero field cooled measurement. The vertical shift is noticed below ~125 K which increases with decreasing temperature and reaches a maximum of 33% at 2 K. The vertical shift is modelled closely using micromagnetic simulations. It is shown that the amount of vertical shift depends on the competition between the relative thicknesses and the anisotropies of the two f…
Hydrogen detection in a reliable, fast, and cost-effective manner is a prerequisite for the large-scale implementation of hydrogen in a green economy. We present thin film Ta$_{1-y}$Pd$_y$ as effective optical sensing materials with extremely wide sensing ranges covering at least seven orders of magnitude in hydrogen pressure. Nanoconfinement of the Ta$_{1-y}$Pd$_y$ layer suppresses the first-order phase transitions present in bulk and ensures a sensing response free of any hysteresis. Unlike other sensing materials, Ta$_{1-y}$Pd$_y$ features the special property that the sensing range can be …
We demonstrate how the configuration and magnitude of a magnetic field, applied during magnetron sputtering of a NiFe/IrMn bilayer, influence the magnetic properties of the structure, such as hysteresis loop shape, coercivity, and exchange bias. Furthermore, we illustrate that it is possible to create a stepwise hysteresis loop in the sample's region with the highest field gradient. The found features can be used for future sensor applications.
Mixed iodine-bromine perovskites used in solar cells undergo below a critical temperature an intrinsic demixing into phases with different iodine-bromine compositions. In addition, under illumination they show nucleation of an iodine-rich phase. We predict from thermodynamic considerations that in mixed iodine-bromine perovskites like MAPb(I$_{1-x}$Br$_x$)$_3$ the interplay of these effects can lead to coexistence of a bromine-rich, iodine-rich, and nearly iodine-pure nucleated phase. This three-phase coexistence occurs in a region in the composition-temperature phase diagram near the critical…
Hysteretic magnetoresistance (MR) is often used as a signature of ferromagnetism in conducting oxide thin films and heterostructures. Here, magnetotransport is investigated in a non-magnetic uniformly La-doped SrSnO3 film grown using hybrid molecular beam epitaxy. A 12 nm La:SrSnO3/2 nm SrSnO3/GdScO3 (110) film with insulating behavior exhibited a robust hysteresis loop in the MR at T < 5 K accompanied by an anomaly at ~ +/- 3 T at T < 2.5 K. Furthermore, MR with the field in-plane yielded a value exceeded 100% at 1.8 K. Using detailed temperature-, angle- and magnetic field-dependent resistan…
Coexistence of ferroelectric and ferrielectric phases in ultrathin antiferroelectric PbZrO3 thin films
Catalan Institute of Nanoscience and Nanotechnology (ICN2)（加泰罗尼亚纳米科学和技术研究所）；School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney（悉尼大学航空航天、机械与机电工程学院）；Institut Català de Recerca i Estudis Avançats (ICREA)（加泰罗尼亚研究与高级研究学院）
Itinerant magnets generally exhibit pressure induced transitions towards non magnetic states. Using synchrotron based X-ray diffraction and emission spectroscopy, the evolution of the lattice and spin moment in the chiral magnet MnGe was investigated in the paramagnetic state and under pressures up to 38 GPa. The collapse of spin-moment takes place in two steps. A first-order transition with a huge hysteresis around 7 GPa transforms the system from the high-spin at ambient pressure to a low-spin state. The coexistence of spin-states and observation of history-depending irreversibility is expla…
The thermodynamics of phase transitions between phases that are size-mismatched but coherent differs from conventional stress-free thermodynamics. Most notably, in open systems such phase transitions are always associated with hysteresis. In spite of experimental evidence for the relevance of these effects in technologically important materials such as Pd hydride, a recipe for first-principles-based atomic-scale modeling of coherent, open systems has been lacking. Here, we develop a methodology for quantifying phase boundaries, hysteresis, and coherent interface free energies using density-fun…
Amorphous ferrimagnetic TbFeCo thin films are found to exhibit exchange bias effect near the compensation temperature by magnetic hysteresis loop measurement. The observed exchange anisotropy is believed to originate from the exchange interaction between the two nanoscale amorphous phases distributed within the films. Here, we present a computational model of phase-separated TbFeCo using micromagnetic simulation. Two types of cells with different Tb concentration are distributed within the simulated space to obtain a heterogeneous structure consisting of two nanoscale amorphous phases. Each ce…
Magnetic properties of epitaxial Fe$_3$O$_4$ films with various crystal orientations and TMR effect in room temperature
Fe $_3$ O $_4$是在室温（RT）下表现出导电性的亚铁磁性尖晶石铁氧体。虽然根据从头计算已经预测该材料是半金属，但是具有Fe $_3$ O $_4$电极的磁性隧道结（MTJ）已经证明了小的隧道磁阻效应。甚至连TMR比率的符号都没有在实验中确定。在这里，我们报告的磁性外延Fe $_3$ O $_4$薄膜与各种晶体取向。薄膜的磁滞曲线显示出明显的晶体取向依赖性。特别地，Fe $_3$ O $_4$（110）膜表现出面内单轴磁各向异性。对于磁滞回线的矩形度，Fe $_3$ O $_4$（111）表现出最大的矩形度。此外，我们还制备了Fe $_3$ O $_4$（110）电极的MTJ，在室温下获得了-12\%的TMR效应。负的TMR比对应于能带计算预测的Fe $_3$ O $_4$的负自旋极化。
