Magnetic properties of pure and Fe doped HoCrO3 thin films fabricated via a solution route

Abstract

Multiferroic properties of orthorhombically distorted perovskite rare-earth chromites, such as HoCrO 3 , are being investigated extensively in recent years. In the present work, we report on the effect of Fe substitution on the magnetic properties in HoCrO 3 thin films. Thin films of nominal compositions with HoCrO 3 and HoCr 0.7 Fe 0.3 O 3 were fabricated via a solution route on platinized silicon substrates. Structural properties of the films were characterized by Xray diffraction and Raman spectroscopy. The surface morphology and cross-sections of the films were examined using scanning electron microscopy. Optical band gaps of these films are found to be 3.45 eV and 3.39 eV, respectively. The magnetization measurement shows that the Néel temperatures (where Cr 3+ orders) for the HoCrO 3 and HoCr 0.7 Fe 0.3 O 3 films are 134 and 148 K, respectively. In a magnetic field of 2 T, the maximum entropy change and relative cooling power, two parameters to evaluate the magnetocaloric properties of a material, were 0.813 J/kg K at 11 K and 21.1 J/kg for HoCrO 3 film, in comparison with 0.748 J/kg K at 15 K and 26.8 J/kg for HoCr 0.7 Fe 0.3 O 3 film. To our knowledge, this is the first work exploring the band gap and magnetocaloric properties of rare-earth chromite thin films. These findings should inspire the development of rare-earth chromite thin films for temperature control of nanoscale electronic devices and sensors in the low temperature region (<30 K).

Facile synthesis and selected characteristics of two-dimensional material composed of iron sulfide and magnesium-based hydroxide layers (tochilinite)

“…The clusters denoted [2Fe-2S] are known to be composed of iron atoms in tetrahedral coordination to sulfur, including two S atoms in peptide molecules, either paramagnetic with spin alignment of Fe 2+ and Fe 3+ cations (S = 1/2) or antiferromagnetic with two Fe 3+ cations (S = 0). [75][76][77][78][79][80] The clusters [1Fe-0S] 2+/3+ with Fe 2+ (S = 2) or Fe 3+ (S = 5/2) in tetrahedral environment of S better agree with the Mo ¨ssbauer spectroscopy findings (Fig. 3), suggesting insignificant alignment of neighboring electron spins in tochilinite.…”

“…A characteristic response frequency and a peak temperature (T p ) can be found at maxima of the imaginary part of the dielectric constant e 00 vs. temperature plots at various frequencies. The temperature dependence of the characteristic frequencies can be described, as a first approximation, by the Arrhenius relation: [79][80][81]…”

“…6 (A) UV-vis-NIR absorption spectra of aqueous colloids of tochilinite synthesized hydrothermally using the proportions of reagents (a) Fe 2, Mg 1.5, S 15, (b) Fe 2, Mg 1.5, S 15, Al 0.5, (c) Fe 2, Mg 1.5, S 15, Li 0.5, (d) Fe 2, Mg 1.5, S 15, Al 0.5, Li 0.5; and dispersed in water. (B) Simplified diagram of the electron levels for Fe2+ cations assuming tetrahedral coordination (the levels for Fe 3+ are not shown), S ligands, and optical transitions in the sulfide layer of tochilinite by analogy with Fe-S cluster in peptides 79,80.…”

Facile synthesis and selected characteristics of two-dimensional material composed of iron sulfide and magnesium-based hydroxide layers (tochilinite)

“…The ac permittivity changes by about three orders of magnitude with the temperature and exhibits a characteristic response frequency at a peak temperature (Tp) for the frequency variation of the imaginary part ``. As a first approximation, the temperature dependence of the characteristic frequency can be described by the Arrhenius relation [72][73][74]:…”

Facile synthesis and selected characteristics of two-dimensional material composed of iron sulfide and magnesium-based hydroxide layers (tochilinite)

“…The ac permittivity changes by about three orders of magnitude with the temperature and exhibits a characteristic response frequency at a peak temperature (T p ) for the frequency variation of the imaginary part ε``. As a first approximation, the temperature dependence of the characteristic frequency can be described by the Arrhenius relation [72][73][74]:…”