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Due to the strong interactions from multiple degrees of freedom at the interfaces, electron-correlated oxide heterostructures have provided a promising platform for creating exotic quantum states. Understanding and controlling the coupling effects at the oxide interface are prerequisites for designing emergent interfacial phases with desired functionalities. Here, we report the dimensional control of the interface coupling-induced ferromagnetic (FM) phase in perovskite-CaRuO3/infinite-layered-SrCuO2 superlattices. Structural analysis reveals the occurrence of chain-type to planar-type structural transitions for the SrCuO2 layer as the layer thickness increases. The Hall and magnetoresistance measurements indicate the appearance of an interfacial FM state in the originally paramagnetic CaRuO3 layers when the CaRuO3 layer is in proximity to the chain-type SrCuO2 layers; this superlattice has the highest Curie temperature of ~75 K and perpendicular magnetic anisotropy. Along with the thickness-driven structural transition of the SrCuO2 layers, the interfacial FM order gradually deteriorates and finally disappears. As shown by the X-ray absorption results, the charge transfer at the CaRuO3/chain-SrCuO2 and CaRuO3/plane-SrCuO2 interfaces are different, resulting in dimensional control of the interfacial magnetic state. The results from our study can be used to facilitate a new method to manipulate interface coupling and create emergent interfacial phases in oxide heterostructures. Harnessing Quantum States: A Breakthrough in Oxide Heterostructures Perovskite transition-metal oxides, known for their complex electron interactions, exhibit unique physical properties like superconductivity and magnetoresistance. However, layering these materials can result in new, unexpected behaviors at their interfaces. This study focuses on a layered structure of perovskite ruthenate and strontium cuprate. The research shows that by controlling the thickness of SCO layers in CRO/SCO superlattices, it is possible to induce ferromagnetism in CRO, which normally does not exhibit this property. The authors conclude that this manipulation of interface coupling can lead to new interfacial phases with potential applications in spintronics. The findings open up possibilities for future research into the control of quantum phases in complex oxide materials. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author. In this paper, we report the dimensional control of the interface coupling-induced ferromagnetic phase in perovskite-CaRuO3/infinite-layered-SrCuO2 superlattices. The Hall and magnetoresistance measurements indicate the appearance of an interfacial ferromagnetic state in the originally paramagnetic CaRuO3 layers when the CaRuO3 layer is in proximity to the chain-type SrCuO2 layers; this superlattice has the highest Curie temperature of ~75 K and perpendicular magnetic anisotropy. Along with the thickness-driven structural transition from chain-type to planar-type of the SrCuO2 layers, the interfacial ferromagnetic order gradually deteriorates and finally disappears. [ABSTRACT FROM AUTHOR]

Barocaloric materials are particularly promising for green and efficient solid-state cooling technology because of their great potential in terms of cooling performance. However, intermetallic materials with outstanding barocaloric effects under low hydrostatic pressure are especially lacking, which has severely delayed the development of barocaloric refrigeration. Here, in a rare-earth intermetallic La-Ce-Fe-Si-H, we achieve a giant specific barocaloric temperature change of 8 K per kbar according to direct measurements of the adiabatic temperature change ΔTBCE under hydrostatic pressure, which is confirmed by a phenomenological transition simulation. This barocaloric strength is significantly better than those in previously reported phase-transitioned alloys. By using a cutting-edge in situ neutron diffraction technique operating under simultaneously varying temperature, magnetic field, and hydrostatic pressure, we reveal that the large isotropic transition volume change in La-Ce-Fe-Si-H plays a crucial role in the giant barocaloric effect. Additionally, we employ Landau expansion theory to demonstrate that the high sensitivity of the transition temperature to the applied pressure produces the sizable ΔTBCE in the itinerant electron metamagnetic transition alloys. Our results provide insight into the development of high-performance barocaloric materials and related cooling systems.A rare-earth intermetallic La-Ce-Fe-Si-H has been directly measured to cool 8 K when it is under a 1 kbar pressure. This barocaloric strength significantly outperforms those in previously reported phase-transitioned alloys. A multifield-dependent neutron diffraction has revealed that the large isotropic transition volume change for La-Ce-Fe-Si-H plays a crucial role in exploring the giant barocaloric effect. [ABSTRACT FROM AUTHOR]

Solid-state refrigeration based on the caloric effect is viewed as a promising efficient and clean refrigeration technology. Barocaloric materials were developed rapidly but have since encountered a general obstacle: the prominent caloric effect cannot be utilized reversibly under moderate pressure. Here, we report a mechanism of an emergent large, reversible barocaloric effect (BCE) under low pressure in the hybrid organic–inorganic layered perovskite (CH3–(CH2)n−1–NH3)2MnCl4 (n = 9,10), which show the reversible barocaloric entropy change as high as ΔSr ∼ 218, 230 J kg−1 K−1 at 0.08 GPa around the transition temperature (Ts ∼ 294, 311.5 K). To reveal the mechanism, single-crystal (CH3–(CH2)n−1–NH3)2MnCl4 (n = 10) was successfully synthesized, and high-resolution single-crystal X-ray diffraction (SC-XRD) was carried out. Then, the underlying mechanism was determined by combining infrared (IR) spectroscopy and density function theory (DFT) calculations. The colossal reversible BCE and the very small hysteresis of 2.6 K (0.1 K/min) and 4.0 K (1 K/min) are closely related to the specific hybrid organic–inorganic structure and single-crystal nature. The drastic transformation of organic chains confined to the metallic frame from ordered rigidity to disordered flexibility is responsible for the large phase-transition entropy comparable to the melting entropy of organic chains. This study provides new insights into the design of novel barocaloric materials by utilizing the advantages of specific organic–inorganic hybrid characteristics.Solid-state coolants: Hybrid crystals deliver big chills at low pressures Materials that can absorb and release heat under low mechanical pressure hold promise for high-efficiency refrigeration technology. Recent studies have shown that significant compression-induced cooling effects at low pressures can be achieved using crystals known as perovskites containing layers of organic chains and metal cations. Yihong Gao from the Chinese Academy of Sciences in Beijing and colleagues have now uncovered the mechanism underlying the thermal response of layered perovskites. Using a combination of x-rays, spectroscopy and theoretical calculations, the team discovered how the crystal structure changes at different temperatures. Their experiments revealed a low-energy phase transition where organic chains transform from rigid states to highly flexible conformations held in place by metallic layers. The large entropy change associated with this transition and its reversible nature could aid in the design of other organic–inorganic solid-state coolants.For the emergent colossal, reversible barocaloric effect in organic–inorganic perovskite hybrids (CH3–(CH2)n−1–NH3)2MnCl4 (n = 9, 10), we successfully grew a single crystal, and the underlying mechanism was determined by high-resolution SC-XRD, IR spectroscopy and DFT calculations. The drastic transformation of organic chains confined to the metallic frame from ordered rigidity to disordered flexibility is responsible for the large phase-transition entropy, which is comparable to the melting entropy of organic chains. The result provides new insights into designing novel barocaloric materials by utilizing the disordering of organic chains of organic–inorganic hybrid materials. [ABSTRACT FROM AUTHOR]