Scaling analysis of magnetic-thermal behaviors in ferromagnetic insulator LaCoO3 thin film
TL;DR: In this paper, the magnetic entropy change (ΔSM) of LaCoO3 (LCO) thin films under various applied magnetic fields were obtained. And they showed that the critical behavior of LCO thin films may involve complex magnetic interactions, which is correlated with a longterm puzzling finding in this system why its Curie point is always around 80 K regardless of the different fabrication methods and conditions used in the film growth.
About: This article is published in Current Applied Physics.The article was published on 2021-08-01. It has received 4 citations till now. The article focuses on the topics: Curie temperature & Phase transition.
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TL;DR: In this article , structural symmetry control of epitaxially strained LaCoO3 thin films has been proposed to enhance the Curie temperature and magnetization of these thin film structures.
Abstract: Ferromagnetic insulators play a crucial role in the development of low‐dissipation quantum magnetic devices for spintronics. Epitaxial LaCoO3 thin film is a prominent ferromagnetic insulator, in which the robust ferromagnetic ordering emerges owing to epitaxial strain. Whereas it is evident that strong spin‐lattice coupling induces ferromagnetism, the reported ferromagnetic properties of epitaxially strained LaCoO3 thin films are highly consistent. For example, even under largely modulated degree of strain, the reported Curie temperatures of epitaxially strained LaCoO3 thin films lie in a narrow range of 80–85 K, without much deviation. In this study, substantial enhancement (≈18%) in the Curie temperature of epitaxial LaCoO3 thin films is demonstrated via crystallographic orientation dependence. By changing the crystallographic orientation of the films from (111) to (110), the crystal‐field energy is reduced and the charge transfer between the Co and O orbitals is enhanced. These modifications lead to a considerable enhancement of the ferromagnetic properties (including the Curie temperature and magnetization), despite the identical nominal degree of epitaxial strain. The findings of this study provide insights into facile tunability of ferromagnetic properties via structural symmetry control in LaCoO3.
1 citations
TL;DR: In this article, the tetragonal distortion of CoO6 octahedra results in a decrease of ΔCF as well as Eg, enhancing the photoconductive performance of LaCoO3 thin films.
1 citations
TL;DR: In this paper, the synergistic effect of biaxially tensile strain and doping yttrium on the structural distortion and photoconductive process of the La1-xYxCoO3 films has been investigated.
TL;DR: In this paper , the synergistic effect of biaxially tensile strain and doping yttrium on the structural distortion and photoconductive process of the La1-xYxCoO3 films was investigated.
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TL;DR: In this article, the magnetocaloric effect along with recent progress and future needs in both the characterization and exploration of new magnetic refrigerant materials with respect to their magnetoric properties are discussed.
1,355 citations
TL;DR: A study of four Gd samples of different purities using ac susceptibility, magnetization, heat capacity, and direct measurements of the magnetocaloric effect in quasistatic and pulse magnetic fields revealed that all techniques yield the same value of the zero-field Curie temperature of 294(1) K as mentioned in this paper.
Abstract: A study of four Gd samples of different purities using ac susceptibility, magnetization, heat capacity, and direct measurements of the magnetocaloric effect in quasistatic and pulse magnetic fields revealed that all techniques yield the same value of the zero-field Curie temperature of 294(1) K. The Curie temperature determined from inflection points of the experimental magnetic susceptibility and heat capacity is in excellent agreement with those obtained from the magnetocaloric effect and Arrot plots. Above 2 T the temperature of this transition increases almost linearly with the magnetic field at a rate of $\ensuremath{\sim}6\mathrm{K}/\mathrm{T}$ in fields up to 7.5 T. The spin reorientation transition, which occurs at 227(2) K in the absence of a magnetic field, has been confirmed by susceptibility, magnetization, and heat-capacity measurements. Magnetic fields higher than 2--2.5 T apparently quench the spin reorientation transition and Gd retains its simple ferromagnetic structure from the ${T}_{C}(H)$ down to $\ensuremath{\sim}4\mathrm{K}.$ The nature of anomaly at $T\ensuremath{\cong}132\mathrm{K},$ which is apparent from ac susceptibility measurements along the $c$ axis, is discussed. The presence of large amounts of interstitial impurities lowers the second-order $\mathrm{paramagnetic}\ensuremath{\leftrightarrow}\mathrm{ferromagnetic}$ transition temperature, and can cause some erroneous results in the magnetocaloric effect determined in pulsed magnetic fields. The magnetocaloric effect was studied utilizing the same samples by three experimental techniques: direct measurements of the adiabatic temperature rise, magnetization, and heat capacity. All three techniques, with one exception, yield the same results within the limits of experimental error.
862 citations
TL;DR: In this paper, the field dependence of the magnetic entropy change can be expressed as ΔSM∆Hn for soft magnetic amorphous alloys, and a master curve behavior for the temperature dependence of ΔSM measured for different maximum fields is proposed.
Abstract: The field dependence of the magnetic entropy change can be expressed as ΔSM∝Hn For soft magnetic amorphous alloys n=1 well below the Curie temperature (TC), n=2 in the paramagnetic range, and n≈075 for T=TC The first value can be explained with simple arguments, n=2 is a consequence of the Curie-Weiss law, but n(TC) deviates from mean field predictions From the Arrott-Noakes equation of state, a relation between n(TC) and the critical exponents has been obtained, showing remarkable agreement with experimental data (for an example alloy, predicted n=072 versus experimental n=073) A master curve behavior for the temperature dependence of ΔSM measured for different maximum fields is proposed
858 citations
TL;DR: In this article, the selection of materials and expected magnetocaloric effects for magnetic cooling applications at elevated temperatures (400-800 K) were discussed for rare earth transition metal compounds such as Sm2Fe17−xCox for this task.
Abstract: Selection of materials and expected magnetocaloric effects are discussed for magnetic cooling applications at elevated temperatures (400–800 K). Various considerations result in the selection of rare earth‐transition metal compounds such as Sm2Fe17−xCox for this task. These materials offer a wide range of suitable magnetic ordering temperatures as a function of x. They also show relatively high effective magnetic moments per volume. Molecular field models are developed for analytically predicting entropy changes at and above the ordering temperature. Concomitant adiabatic cooling ΔT is accordingly computed for these compounds near the ordering temperatures. It is found that for a family of compounds ΔT values increase somewhat with increasing ordering temperatures due to the decreasing influence of the lattice heat capacity at higher temperatures. Adiabatic cooling of ΔT=−7.5 K at 70 kOe to ΔT=−9.2 K at 70 kOe is predicted for materials Y2Fe17−xCox near their Curie points of 300 and 600 K, respectively (c...
695 citations
TL;DR: In this article, a detailed procedure for constructing the phenomenological universal curve for the magnetic entropy change is presented, together with the exponents which control the field dependence of the different magnetocaloric-related magnitudes.
Abstract: The detailed procedure for constructing the recently proposed phenomenological universal curve for the magnetic entropy change is presented, together with the exponents which control the field dependence of the different magnetocaloric-related magnitudes. Practical applications of the universal curve are also outlined: as a simple screening procedure of the performance of materials, as a method for making extrapolations to temperatures or fields not available in the laboratory, for the reduction of the experimental noise, for correcting the influence of non-saturating conditions, or as a way to eliminate the contribution of minority magnetic phases, among others.
507 citations