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The characteristic size of the magnetocaloric materials in magnetic refrigerators, thermomagnetic regenerators and energy harvesters is usually down to micrometer and nanometer length scales, which provides the largest possible contact surface area to the heat transfer liquid. Therefore, it is pivotal to investigate the structural, magnetic and magnetocaloric properties of magnetocaloric materials at micrometer and nanometer length scales. In the present study, we have successfully fabricated MnCoGe-based thin films using the pulsed laser deposition (PLD) technique. The as-deposited film shows a dense surface, homogeneous chemical distribution and a preferred orientation along the c -axis of the hexagonal Ni 2 In-type structure. In-situ temperature-dependent X-ray diffraction measurements on the as-deposited films reveal an irreversible structural degradation above 300 °C due to the considerable evaporation of the Mn atoms, which causes the formation of microscale pores in the films. The thermomagnetic behavior of the film annealed at 250 °C displays a reversible second-order ferromagnetic transition of the hexagonal phase at Curie temperature T C = 275 K, and a first-order hexagonal-orthorhombic structural transition below 200 K. The decoupling of the magnetic and structural transitions brings reversible magnetocaloric effect with the entropy change ΔS values of 2.5 J/(kgK) and the refrigeration capacity reaching 89 J/kg in Δμ 0 H = 5 T, which are comparable to other reported magnetocaloric thin films. Moreover, antiferromagnetic coupling in the low-temperature orthorhombic phase was observed, which has rarely been reported in the MnCoGe-based bulk alloys. The different magnetic ground states between the thin film and the bulk alloys may be originated from the strain effect imposed by the Al 2 O 3 substrate. Consequently, this work not only provides insights into the structural, magnetic and magnetocaloric properties of the MnCoGe-based alloys at a nanometer length scale, but also offers a new idea for tailoring the multifunctional properties for this material family. [ABSTRACT FROM AUTHOR]

In an effort to explore new electronic devices with multiple functionalities, there are numerous studies of depositing perovskite oxides on flexible substrates to replace rigid silicon‐based wafer in device applications. In this study, the growth of pseudocubic SrRuO3 single‐crystal thin film on a transparent and flexible muscovite is established. The experimental results confirm that the Curie temperature TC and the magnetic properties can be effectively tuned via the mechanical strain due to the facilitation of flexible substrate. It is found that the tensile strain increases while the compressive strain decreases the spontaneous magnetization for the thin film suffering the same ±0.24% strain. Based on the study of critical behavior, the critical exponents β = 0.543(19) and γ = 1.262(1) with the critical temperature TC = 159.04(5) K and TC = 159.10 K, respectively, are obtained by the modified Arrott plot. The set of critical exponents matches well with Widom scaling relation and the scaling equation, indicating these critical exponents are intrinsic for SrRuO3 thin films. Moreover, it is achieved that the SrRuO3 thin films exhibit a long‐range interaction coupled with 3D‐Heisenberg type. [ABSTRACT FROM AUTHOR]

Apart from the impact of different substrates on epitaxial thin films due to lattice constant mismatches, the properties of epitaxial thin films are also influenced by the same substrates with different crystal orientations. Herein, the (111)‐oriented SrTiO3 (STO) substrates are used to fabricate the LaCoO3 (LCO) epitaxial thin films rather than the more common (001)‐oriented STO substrates. It undergoes one paramagnetic–ferromagnetic phase transition around 50 K. This phase transition is similar to the previously observed for (001)‐LCO/STO, but the Curie temperature (Tc) is significantly lower than the previously reported 80 K. To investigate the decrease of Tc and gain further insight into the phase transition, the critical behavior analysis of thin film is performed. The critical exponents are determined to be β = 1.591(3) and γ = 0.937(1) by reconstructing a modified Arrott plot, and the reliability of these exponents is confirmed by the Widom scaling relation. Using the renormalization group theory approach, it is discovered that the film has a long‐range magnetic interaction with space dimensionality d = 2 and spin dimensionality n = 1, and the magnetic exchange interaction decays J(r)≈r−2.4473. [ABSTRACT FROM AUTHOR]

Polycrystalline La 0.825 Sr 0.175 MnO 3 was prepared by solid state reaction method. It exhibits a ferromagnetic–paramagnetic phase transition at T C ∼ 286 K. The intrinsic magnetic properties were clarified by the scaling theory and the isothermal magnetization measured around T C. Based on the modified Arrott plot, Kouvel–Fisher method and Widom relation, the critical exponents are determined to be β = 0. 308 (7) , γ = 1. 065 (8) , δ = 4. 457 (17). Normalization of the critical exponents shows that the extended exchange interaction decays with J ∼ r − 4. 861 , consistent with Tricritical mean field model. Rhodes–Wohlfarth ratio P C / M S >1 suggests that La 0.825 Sr 0.175 MnO 3 is completely itinerant ferromagnet. [Display omitted] • La 0.825 Sr 0.175 MnO 3 shows FM–PM phase transition at 286 K. • Its critical exponents (β = 0.308, γ = 1.065) were determined by the scaling theory. • Its phase transition belongs to Tricritical mean field model. [ABSTRACT FROM AUTHOR]

We have studied the evolution of Griffiths phase and the magnetic ordering state in the intermetallic compound LaCeCo 7. A ferromagnetic-like ordering phase is built up at 260 K but an anomalous magnetic susceptibility related to the Griffiths phase occurs in 300 K. The studies of critical behavior confirm that LaCeCo 7 exhibits a second-order paramagnetic-ferromagnetic phase transitions. The critical exponents of β = 0.665, γ = 1.151, and δ = 2.728 determined by the magnetic field dependence on magnetic entropy change method deviate a little from the theoretical estimated long-range mean-field model (β = 0.5, γ = 1.0, and δ = 3.0). This result implies that the disorder effect in the intermetallic LaCeCo 7 possibly plays a key role on the anomalous critical behavior and the establishment of magnetic ordering phase. [ABSTRACT FROM AUTHOR]

• The critical behavior of (Ce 0.65 Pr 0.35) 2 Co 7 alloy has been clarified with different methods. • The accurate Curie temperature of 214 K has been confirmed by the Arrott plot and ac magnetic susceptibility. • The magnetic coupling of (Ce 0.65 Pr 0.35) 2 Co 7 alloy belongs to long-range FM interaction. Clarification of magnetic phase transition nature and critical behavior is an essential step in the development of new magnetic functional materials. In this work, we studied critical properties of intermetallic compound (Ce 0.65 Pr 0.35) 2 Co 7 by bulk dc magnetization around the paramagnetic to ferromagnetic phase transition. It exhibits a second-order magnetic phase transition with T C = 214 K. Critical exponents β = 0.546(5) and γ = 1.054(5) are obtained by the modified Arrott plot, whereas δ = 2.843 is obtained by a critical isotherm analysis at T C. These critical exponents not only obey the Widom relation δ = 1 + γ / β , but also collapse the isothermal magnetization M-H-T data into two branches below and above T C following the single scaling equation M(H, ε) = ε β f ± (H/ ε β + γ ). Although the obtained exponents are close to the theoretical values of mean-field model, a noticeable deviation unable to be ignored, indicating the existence of localized magnetic interaction which competes with a long-range ferromagnetic state. Our results will establish a sound theoretical basis for understanding the complex magnetic interaction in the light rare earths ternary alloy. [ABSTRACT FROM AUTHOR]