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Electron paramagnetic resonance (EPR) studies were performed on La 0.88 Sr 0.12 MnO 3 (LSMO) nanocrystalline together with the measurement of its magnetization. Various spectrum parameters including line width, effective g-value and double-integrated intensities have been analyzed in detail. We found nonlinear behavior occurred in the inverse susceptibility far above the Curie temperature T C, indicating short-range ferromagnetic (FM) clusters and Griffiths-like phase behavior in the paramagnetic (PM) phase. Based on the variation of EPR spectra, except for a typical PM resonance peak, an extra resonance signal was observed in the lower field region and developed as temperature decreased from 320 K to 110 K, which gave a direct evidence of the existence of FM cluster in the PM region of LSMO nanocrystalline. We proposed that the appearance of the Griffiths phase was due to the short FM correlation in the PM regime enhanced by surface spin ordering., (© 2024. The Author(s).)

Monolayer (ML) NiCl 2 exhibits a strong biquadratic exchange interaction between the first neighboring magnetic atoms ( B 1 ), as demonstrated by the spin spiral model in J. Ni et al. , Phys. Rev. Lett. , 2021, 127 , 247204. This interaction is crucial for stabilizing the ferromagnetic collinear order within the ML NiCl 2 . However, they neither point out the role of B 1 nor discuss the dispersion relation from spin orbit coupling (SOC) in the spin spiral. As we have done in this work, these parameters might theoretically potentially be derived directly by fitting the calculated spin spiral dispersion relation. Here, we draw attention to the fact that B 1 is equivalent to half of J 3 in Heisenberg linear interactions and that the positive B 1 partially counteracts the negative J 3 's impact on the spin spiral to make the ML NiCl 2 ferromagnetic. The comparatively small J 3 + 1/2 B 1 from the spin spiral led us to believe that J 3 could be substituted by B 1 , yet it still exists and plays a crucial function in magnetic semiconductors or insulators. The dispersion relation, which we also obtain from SOC, displays weak antiferromagnetic behavior in the spin spiral.

Based on density functional theory calculations, we elucidated the tunability of the atomic structures and magnetic interactions of Co/Pt 3 interface (one layer of hcp(0001) Co and three layers of fcc(111) Pt) and thus the skyrmion sizes using strain. The dispersion relations of the spin spiral in the opposite directions, E( q ) and E(- q ), were evaluated based on generalized Bloch equations. Effective exchange coupling (EC) and Dzyaloshinsky-Moriya interaction (DMI) parameters between different neighbors J i and d i at different lattice constants were derived by fitting the resulting spin spiral dispersion E( q ) to EC model with DMI and E( q )-E(- q ) formula, respectively. We observed an increase in DMI and a significant decrease in EC with an increase in strain. Hence, the size of Néel-type skyrmions determined by the ratio of EC/DMI can be controlled by applying strain, leading to an effective approach to tailor the formation of skyrmion lattices by inducing slight structural modifications on the magnetic thin films., Competing Interests: The authors declare no competing interests., (© 2022.)

Tricritical phenomenon appearing in multiple phases is a fundamental and attractive issue in condensed-matter physics. In this work, a field-modulated tricritical phenomenon is realized in single-crystal PrCu 9 Sn 4 . The magnetization under variable directions of field indicates strong magnetic anisotropy in PrCu 9 Sn 4 , which reveals ferromagnetic coupling for H // c . A paramagnetic-to-ferromagnetic magnetic transition occurs with H // c at T C = 11.7 K, which is evidenced to be of a first-ordered type. The systematical study of the critical behavior gives that β = 0.195(8), γ = 0.911(1), and δ = 0.0592(1) for H // c consistent with a tricritical mean-field model, which suggests a field-modulated tricritical phenomenon. A detailed H - T phase diagram around the tricritical point (TCP) is constructed for single-crystal PrCu 9 Sn 4 for H // c , where ferromagnetic state, forced ferromagnetic phase and paramagnetic state meet at the TCP ( H tr = 799 kOe, T tr = 11.3 K). The single-crystal PrCu 9 Sn 4 supplies a platform to deep investigate the field-modulated magnetic couplings and tricritical phenomenon., (© 2022 IOP Publishing Ltd.)

Piezoelectric sensors can be utilized in Lamb-wave-based structural health monitoring (SHM), which is an effective method for aircraft structural damage detection. However, due to the inherent stiffness, brittleness, weight, and thickness of piezoelectric ceramics, their applications in aircraft structures with complex curved surfaces are seriously restricted. Herein, we report a flexible, light-weight, and high-performance BaTiO 3 :Sm 2 O 3 /SrRuO 3 /SrTiO 3 /mica film sensor that can be used in high-temperature SHM of aircraft. Enhanced ferroelectric Curie temperature (487 °C) and piezoelectric coefficient d 33 (120-130 pm/V) are achieved in BaTiO 3 , which can be attributed to the tensile strain developed by stiff Sm 2 O 3 nanopillars. Stable ferroelectricity and piezoelectricity are retained up to 150 °C. The flexible BaTiO 3 :Sm 2 O 3 /SrRuO 3 /SrTiO 3 /mica film is validated as an ultrasonic sensor with high sensitivity and stability for damage monitoring on aircraft structures with the curved surface ranging from 25 to 150 °C. Our work demonstrates that flexible and light-weight BaTiO 3 :Sm 2 O 3 /SrRuO 3 /SrTiO 3 /mica film sensors can be employed as high-temperature piezoelectric sensors for real-time SHM of aircraft structures with complex curved surfaces.

High-quality epitaxial LaCoO 3 (LCO) thin films have been deposited on SrTiO 3 (STO) substrates with pulsed laser deposition (PLD). We find that the LCO films undergo a typical ferromagnetic-paramagnetic (FM-PM) phase transition at ∼80 K. To understand the nature of magnetic phase transition, various methods, including the modified Arrott plot and critical isotherm analysis, were used to determine the critical exponents, which are β = 0.754(1) with a Curie temperature T C = 79.8(8) K and γ = 1.52(2) with T C = 79.9(2) K. The reliability of these critical exponents was confirmed using the Widom scaling relation and the scaling hypothesis. Further analysis revealed that the spin coupling within the LCO films exhibits two-dimensional (2D) long-range magnetic interaction and the magnetic exchange distance decays as J(r) ∼r -(3.46) . Our critical behavior analysis may shed new light on the further understanding of the origin of FM and the relatively fixed T C in LCO thin films.

The temperature-dependent spin-reorientation transition (SRT) and spin interaction mechanism of bulk TmFeO3 were studied by the electron paramagnetic resonance (EPR) method. The combined experimental results of magnetic curves and EPR spectra confirmed that there is an antiferromagnetic transition at 85 K with a reentering ferromagnetic state due to the spin-reorientation behavior. In the high-temperature region of T > 90 K, there are three distinct resonance peaks in the EPR spectrum, which indicates the presence of multiple magnetic phases (canted antiferromagnetic, weak ferromagnetic, and paramagnetic phases). In the low-temperature region (T < 85 K), the temperature dependence of the EPR linewidth, effective g-factor, and intensity can be used to infer a strong spin-lattice correlation. Different magnetic interactions such as Fe3+-Fe3+, Fe3+-Tm3+, and Tm3+-Tm3+ lead to a paramagnetic-canted antiferromagnetic phase at T > 85 K, with SRT between 85-65 K and ferromagnetic interaction at the lower temperature, respectively. Above 90 K, we find that the spin relaxation mechanism is determined by the mixture of spin-spin and spin-lattice interactions. Below 85 K, the transverse relaxation rate increases with the decrease in temperature, which is consistent with the weakening of the fluctuating internal field in this temperature region. This EPR detection provides a new method to clarify the strong spin coupling in antiferromagnetic materials.

Generally, magnetic anisotropy is a common feature of a layered magnetic material, the exploration of which plays a key role in understanding the intrinsic magnetic couplings. In this work, we have studied the field-induced magnetic transitions for layered YbNi 3 Al 9 as the external magnetic field is applied perpendicularly ([Formula: see text]) and parallel (H//c) to the c-axis. We find that two independent universal curves of magnetic entropy change [[Formula: see text]] can be fitted out for [Formula: see text] and H//c, respectively. According to the universality principle of scaling, the extra magnetic entropy changes ([Formula: see text] and [Formula: see text]) caused by the field-induced magnetic phase transitions can be obtained for [Formula: see text] and H//c. The two-dimensional [Formula: see text] plots as functions of field and temperature are constructed, which clearly reveal the evolutions of the magnetic entropy changes resulted from the two different field-induced magnetic phase transitions. It is suggested that the [Formula: see text] for [Formula: see text] with the maximum at (3.2 K, 4.1 kOe) originates from a field-modulated helicoidal spin-texture. However, the [Formula: see text] for H//c with the maximum at (3.4 K, 13.8 kOe) stems from a field-induced canted antiferromagnetic state.

Transparent and flexible electronic devices are highly desired to meet the great demand for next-generation devices that are lightweight, flexible, and portable. Transparent conducting oxides (TCOs), such as indium-tin oxide, serve as fundamental components for the design of transparent and flexible electronic devices. However, indium is rare and expensive. Herein, we report the fabrication of low-cost perovskite SrVO 3 TCO films on transparent and flexible mica substrates and further demonstrate their utilization as a TCO electrode for building a transparent, flexible, and self-powered perovskite photodetector. Superior stable optical transparency and electrical conductivity are retained in SrVO 3 after bending up to 10 5 cycles. Without an external power source, the constructed all-perovskite photodetector exhibits a high responsivity (42.5 mA W -1 ), fast response time (3.09/1.23 ms), and an excellent flexibility and bending stability after dozens of cycles of bending at an extreme 90° bending angle. Our results demonstrate that low-cost and structure-compatible transition metal-based perovskite oxides, such as SrVO 3 , as TCO electrodes have huge potential for building high-performance transparent, flexible, and portable smart electronics.

We report the physical properties of Eu-doped bulk TmFeO 3 through X-ray diffraction, magnetic susceptibility (χ), Raman scattering and X-ray absorption spectroscopy (XAS) study, which shows a similar orthorhombic structure with the Pbnm space group as TmFeO 3 . Magnetic measurement on Eu-doped TmFeO 3 provides evidence for spin reorientations of Fe 3+ . Further, the Raman spectra of Eu 3+ doped TmFeO 3 show significant changes in Raman modes as a function of temperature, which are evidence for strong spin-lattice interaction. From the XAS spectra, the L-edge of Fe provides information on the valence state of Fe, whereas the K-edge of oxygen shows that the compound has a strong influence on the hybridization of the O(2p) state with the 3d states of Fe.

The magnetization of Mn-intercalated layered MnNb 3 S 6 single crystal has been systematically investigated. The angle-dependent magnetization ([Formula: see text], [Formula: see text], and [Formula: see text]) displays that the magnetization of MnNb 3 S 6 with [Formula: see text] is much stronger than that with H//c, but no magnetic anisotropy within the ab-plane. In addition, a field-induced magnetic phase transition is found when [Formula: see text]. The investigation of the critical behavior gives the critical exponents [Formula: see text], [Formula: see text], and [Formula: see text] with [Formula: see text] K, which belong to the universality class of three-dimensional Heisenberg model. The critical behavior and exponents indicate that the magnetic coupling in MnNb 3 S 6 is of an isotropic short-range type. Based on universality scaling, the H  -  T phase diagram with [Formula: see text] is constructed. The magnetic behaviors and phase diagram of MnNb 3 S 6 are analogous to those of CrNb 3 S 6 which exhibits a chiral magnetic soliton lattice.

Magnetic and electronic transport properties of perovskite manganite La 0.6 Er 0.1 Sr 0.3 MnO 3 have been thoroughly examined through the measurements of magnetization, electron paramagnetic resonance(EPR), and resistivity. It was found that the substitution of Er 3+ for La 3+ ions introduced the chemical disorder and additional strain in this sample. An extra resonance signal occurred in EPR spectra at high temperatures well above T C gives a strong evidence of electronic phase separation(EPS). The analysis of resistivity enable us to identify the polaronic transport mechanism in the paramagnetic region. At low temperature, a new ferromagnetic interaction generates in the microdomains of Er 3+ -disorder causing the second increase of magnetization. However, the new ferromagnetic interaction does not improve but decreases electronic transport due to the enhancement of interface resistance among neighboring domains. In view of a really wide temperature region for the EPS existence, this sample provides an ideal platform to uncover the evolution law of different magnetic structures in perovskite manganites.

The cubic B20 compound FeGe, which exhibits a near room temperature skyrmion phase, is of great importance not only for fundamental physics such as nonlinear magnetic ordering and solitons but also for future application of skyrmion states in spintronics. In this work, the critical behavior of the cubic FeGe is investigated by means of bulk dc-magnetization. We obtain the critical exponents (β = 0.336 ± 0.004, γ = 1.352 ± 0.003 and β = 5.276 ± 0.001), where the self-consistency and reliability are verified by the Widom scaling law and scaling equations. The magnetic exchange distance is found to decay as r(-4.9), which is close to the theoretical prediction of 3D-Heisenberg model (r(-5)). The critical behavior of FeGe indicates a short-range magnetic interaction. Meanwhile, the critical exponents also imply an anisotropic magnetic coupling in this system.