Multiferroic magnetoelectric (ME) materials and their device applications have gained significant attention over the past decades due to their potential for next-generation nonvolatile memory and spintronic technologies. Among these, strontium-doped lanthanum manganites, La[Formula: see text]SrxMnO3, particularly in the composition range [Formula: see text], are of great interest owing to their colossal magnetoresistive (CMR) behavior, which arises from a delicate interplay between structural, electronic, and magnetic degrees of freedom. La[Formula: see text]Sr[Formula: see text]MnO3 (LSMO), which exhibits a paramagnetic (PM)-insulating state at room temperature and undergoes a ferromagnetic (FM)-metallic transition near 212[Formula: see text]K, has been integrated with a lead-free ferroelectric perovskite, Ba[Formula: see text]Ca[Formula: see text]Zr[Formula: see text]Ti[Formula: see text]O3 (BCZT), to fabricate a multiferroic heterostructure using the Pulsed Laser Deposition (PLD) technique. The heterostructure demonstrates a clear magneto-electric (ME) coupling, where both external magnetic fields and electric field-induced ferroelectric polarization modulate the magneto-transport transition temperature ([Formula: see text] [Formula: see text]K) of the LSMO layer. Comprehensive investigations reveal that ferroelectric polarization switching in the BCZT layer effectively alters the interfacial electronic structure via orbital hybridization and charge carrier redistribution, enabling nonvolatile modulation of magnetization in the LSMO layer, as evidenced by Hall resistivity measurements as a function of magnetic field. This work provides critical insights into strain-mediated and polarization-driven magnetoelectric interactions, presenting a promising pathway toward the realization of electrically tunable, nonvolatile magnetic memory devices based on multiferroic heterostructures.

Caloric effects allow for temperature control through adiabatic application of external fields and are actively explored for solid-state refrigeration. The common wisdom is that the application of ultrahigh fields enhances the effects, thus providing a route to their practical applications. Using the ferroelectric relaxor (Ba, Ca)(Ti, Zr)O-3, we demonstrate that in ferroics, which are the prime candidates for such application, this is not true in general and that caloric effects can be enhanced through the reduction of the applied field. The explanation of such a counterintuitive response is in the dependence of the electrocaloric effect on the effective poling field that can be regarded as a "hidden" variable of the caloric effects.

We report on the enhanced Curie temperature and magnetic anisotropy observed in the temperature dependence of magneto-optic Kerr effect (MOKE) in epitaxial Ni films grown on single-crystal c-cut sapphire Al2O3 (0001) substrates. X-ray diffraction (XRD) revealed the epitaxial growth of Ni (1 1 1) on Al2O3 (0001) substrate while XRD azimuthal scans indicated the presence of 60 degrees -rotated twin-crystal structures of fcc Ni in ABC...and ACB... stacking in the Ni/Al2O3 (0001) film. Twin-crystal structures were also revealed from the surface morphology of the Ni (111) layer in the Ni/Al2O3 (0001) film. MOKE hysteresis loops indicated higher Kerr remanence with lower coercivity for the Ni/Al2O3 (0001) film as compared to the polycrystalline Ni film grown on Si (100) substrate under the same conditions. Azimuthal MOKE hysteresis loops confirmed the presence of 2-fold in-plane magnetic anisotropy in the Ni/Al2O3 (0001) film. Temperature dependent MOKE measurements in the range of 300- 680 K revealed a power-law dependence of the Kerr remanence similar to magnetization. The Curie temperature (TC) of the Ni/Al2O3 film was found to be almost 10 K higher than bulk Ni. In-and out-of-plane magnetization revealed a uniaxial perpendicular magnetic anisotropy with the easy axis along the Ni/Al2O3 film plane. The calculated values of the anisotropy constants revealed a high degree of magnetocrystalline anisotropy in the epitaxial Ni/Al2O3 (0001) film. A close correlation of MOKE and magnetization hysteresis loops indicated similar surface and volume magnetic behaviors in the thin films. The enhanced temperature dependent MOKE, magnetocrystalline anisotropy and magnetization could be attributed to the twin-crystal structures in the epitaxial Ni/Al2O3 film.

A large electrocaloric effect is reported in a strain-engineered Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) thin film heterostructure driven by the near room-temperature electro-structural phase transition. An epitaxial BCZT/La0.7Sr0.3MnO3 (BCZT/LSMO) heterostructure was grown on a single-crystal SrTiO3 (100) substrate using pulsed laser deposition. In-depth x-ray diffraction and x-ray spectroscopic analyses revealed the single-crystalline nature and stoichiometric growth of the heterostructure. Both temperature dependent x-ray diffraction and dielectric measurements revealed a broad second-order-type phase transition near 430 K in the BCZT/LSMO heterostructure. From detailed theoretical analyses of the experimental data, it was confirmed that the phase transition around 430 K is second-order in nature, unlike the first-order transition observed in bulk BCZT materials. Thermodynamic analyses of polarization revealed an unprecedently large adiabatic temperature change of 13.5 K at 430 K under a field change of 1000 kV cm−1, hitherto unobserved in a lead-free material. Extremely broad adiabatic temperature change ΔT(T) curves over a wide working range of temperatures (330 K < T < 480 K) resulted in enhanced relative cooling powers, which are higher than those reported so far in most electrocaloric materials. We propose that an interfacial strain-induced enhanced tetragonal distortion of the BCZT layer gives rise to these large electrocaloric effects in the BCZT/LSMO heterostructure system. The demonstration of a large electrocaloric effect in the lead-free BCZT thin film may open up new pathways toward the design of artificial heterostructures for eco-friendly solid-state cooling applications.

We have studied the effect of doping of both magnetic (Co) and nonmagnetic (Mg) ions at the Cu site on phase transition in polycrystalline α-Cu2V2O7through structural, magnetic, and electrical measurements. X-ray diffraction reveals that Mg doping triggers an onset ofα- toβ-phase structural transition in Cu2-xMgxV2O7above a critical Mg concentrationxc= 0.15, and both the phases coexist up tox= 0.25. Cu2V2O7possesses a non-centrosymmetric crystal structure and antiferromagnetic ordering along with a non-collinear spin structure in theαphase, originated from the microscopic Dzyaloshinskii-Moriya interaction between the neighboring Cu spins. Accordingly, a weak ferromagnetic (FM) behavior has been observed up tox= 0.25. However, beyond this concentration, Cu2-xMgxV2O7exhibits complex magnetic properties. A clear dielectric anomaly is observed in α-Cu2-xMgxV2O7around the magnetic transition temperature, which loses its prominence with the increase in Mg doping. The analysis of experimental data shows that the magnetoelectric coupling is nonlinear, which is in agreement with the Landau theory of continuous phase transitions. Co doping, on the other hand, initiates a sharpαtoβphase transition around the same critical concentrationxc= 0.15 in Cu2-xCoxV2O7but the FM behavior is very weak and can be detected only up tox= 0.10. We have drawn the magnetic phase diagram which indicates that the rate of suppression in transition temperature is the same for both types of doping, magnetic (Co) and nonmagnetic (Zn/Mg).

Dielectric relaxation in ferroelectric perovskites can result from different inherent chemical and charge disorders within their crystal structures. Despite several theories on dielectric relaxations, the relationship between the concentration of oxygen vacancy (V-o) and dielectric relaxation has not been studied in perovskite oxide thin films. In this work, we report a systematic investigation on the influence of the V-o's s on the dielectric relaxation of Ba0.8Ca0.15Ti0.9Zr0.1O3 (BCZT) epitaxial thin films grown with La0.7Sr0.3MnO3 (LSMO) top and bottom electrodes on single-crystal SrTiO3 (100) substrates using pulsed laser deposition. The ambient oxygen pressures during film growth were systematically varied to control the concentration of V-o in the epitaxial BCZT thin films. Low ambient oxygen pressure was found to enhance the tetragonality of the BCZT films and a systematic decrease in the tetragonality was observed at high oxygen pressure conditions as evidenced from x-ray diffraction (XRD) studies. Temperature dependent XRD analyses indicated a low-temperature anomaly near similar to 160 K in the BCZT/LSMO heterostructures. Low-temperature dielectric measurements revealed relaxor dielectric response with broad frequency dependence of the dielectric constant. It is proposed that the low-temperature dielectric relaxation is possibly caused by dipolar clusters that are formed by the aggregation of correlated V-o-induced dipolar defects within the films deposited under different ambient oxygen pressures. High-resolution transmission electron microscopy suggested the presence of the nanometer-sized V-o clusters as represented by the structural defects of average diameters of similar to 5 nm in the BCZT films grown at variable ambient oxygen pressure. Activation energies of the aforesaid dipolar clusters, obtained from the Vogel-Fulcher fitting of the dielectric dispersion, showed a gradual increase in magnitude, as well as decreasing freezing temperatures, with decreasing concentrations of V-o in the BCZT films. From the theoretical analysis of the experimental data, it is postulated that the presence of the V-o-induced dipolar defects affects the low-temperature dielectric relaxation in the BCZT thin films. This work significantly extends the understanding of V-o-mediated dielectric relaxor behavior in complex perovskite oxide films.

An enhanced magnetocaloric effect is being reported in a strain-engineered ferrite-manganite heterostructure driven by a low temperature magnetostructural phase transition. An ultrathin (similar to 20 nm) epitaxial CoFe2O4/La0.7Sr0.3MnO3 (CFO/LSMO) heterostructure was grown on single crystal MgO (100) substrate using pulsed laser deposition. Both temperature dependent x-ray diffraction and magnetization measurements revealed a broad second-order-type magnetostructural phase transition near around 80 K in the CFO/LSMO heterostructure. From detailed theoretical analysis of the experimental data it is confirmed that the phase transition around 80 K is second-order in nature, unlike the first-order transition observed in the bulk CFO materials. Thermodynamic analyses of magnetization reveal extremely broad isothermal entropy changes Delta S(T) about a wide range of temperatures (40 < T < 160 K) resulting in enhanced relative cooling powers which are higher than those reported so far on most magnetocaloric materials. We propose that an interfacial strain-induced magnetostructural coupling of the CFO layer with the underlying LSMO layer gives rise to these hitherto unobserved enhanced magnetocaloric effects in the CFO/LSMO heterostructure system. The work provides fundamental insight into the low temperature phase transitions in ferrite-manganite thin films and adds on to the design of artificial heterostructures with novel and enhanced magnetocaloric properties.

Perovskite oxides show an amazing diversity of electronic and magnetic properties along with a myriad of structural variants and phase transitions. Large thermal changes may be driven near the ferroic phase transitions in perovskite oxides using magnetic, electric, and stress fields to manipulate conjugate order parameters. The ensuing magnetocaloric, electrocaloric, and mechanocaloric effects can be utilized for environment-friendly and high-efficiency solid-state cooling applications. In this review the details of these caloric effects in perovskite oxides both from a chronological perspective and from the viewpoint of the recent advances in multiple caloric phenomena are described. The authors highlight the role of interfaces in oxide thin films for the different caloric effects and address some of the outstanding challenges for the fundamental understanding and practical implementation of perovskite oxides in solid state refrigeration.

Atrial natriuretic peptide (ANP) inhibits and aldosterone (ALDO) stimulates Na conductive transport. Therefore, the effects of ANP and its second messenger cGMP on mineralocorticoid receptor (MR) function in rat colon surface and crypt cells were examined. 100 nM 8-Br-cGMP decreased surface [3H]ALDO binding by 42 +/- 4% but increased crypt [3HvALDO binding by 52+/-16%. ANP decreased surface [3H]ALDO binding by approximately 50% after a 2.5-h lag period but had no effect on crypt ALDO binding. ANP and cGMP rapidly (< 15 min) inhibited surface cell ALDO-induced MR nuclear translocation but did not affect crypt MR nuclear translocation. Inhibition of cGMP-dependent protein kinase with KT5823 blocked the inhibitory effects of ANP and 8-Br-cGMP on surface cell ALDO binding and MR nuclear translocation. In crypt, KT5823 increased baseline [3H]ALDO binding but did not inhibit the stimulatory effect of exogenous cGMP. DEAE-cellulose chromatography and gel mobility shift assay showed that ANP did not inhibit surface MR activation. ANP inhibited ALDO stimulated short circuit current in distal colon. These data demonstrate cell-specific regulation of MR function. In surface cells, ANP rapidly inhibits MR nuclear translocation and ALDO-induced short circuit current. ANP inhibition of MR function may be an additional mechanism of ANP antagonism of Na reabsorption.

The Dorsalis Pedis artery (DPA) is an often overlooked but important artery that can be utilized for limb salvage surgery. It is especially useful in the diabetic patient in whom disease at the level of the bifurcation of the popliteal artery is common. The unique anatomic location and communication with the pedal arch makes the DPA a good outflow vessel. Surg. Gynecol. Obstet. 105 :401–405 (Verta, 1982, Ascer, 1988 J. Vasc. Surg., 8 :434–441; Harris, 1989, Arch Surg., 124 :1232–1235). © 1992 Wiley‐Liss, Inc.