Comparison of the dielectric and magnetocaloric properties of bulk and film of GdFe0.5Cr0.5O3

Abstract

Reported here is a comparison of the magnetic, magnetocaloric, and dielectric properties of 50% iron substituted GdCrO3 (GdFe0.5Cr0.5O3) bulk pellet and 960 nm thick film of GdFe0.5Cr0.5O3 (GFCO). The 960 nm film was synthesized on a platinized-silicon substrate by chemical solution deposition and spin-coating methods. The X-ray diffraction scans of the bulk sample and the film as well as the morphology of the film as examined by the field-emission scanning electron microscope indicate phase-pure and polycrystalline nature of these samples. X-ray photoelectron spectroscopy was used to determine the valence states of Gd, Fe, and Cr. The temperature dependence of the dielectric constant from 225 to 700 K shows peaks at TC = 525 K for the bulk and ∼450 K for the film due to ferroelectric to paraelectric transitions, since electric polarization vs electric field hysteresis loops are observed at room temperature. The dielectric studies in the bulk GFCO for T > TC indicate a relaxor-like behavior. The measurements of the magnetization (M) of the samples as a function of temperature (5–350 K) and magnetic field (H) up to 7 T (=70 kOe) depict hysteresis behavior at low temperatures due to the canted antiferromagnetic order of Fe3+/Cr3+ below the Néel temperature of ∼275 K. The M vs H isotherms at various temperatures are used to determine and compare the magnetic entropy change (−ΔS) and relative cooling power (RCP) of the two samples, yielding (−ΔS) = 30.7 J/kg K (18.8 J/kg K) and RCP = 566.5 J/kg (375 J/kg) for the bulk (960 nm film) samples of GFCO at 7 K and 7 T, respectively. The plot of RCP vs T shows that magnetic cooling for this system is most effective for T < 30 K. Comparatively smaller magnitudes of (−ΔS) and RCP for the film vis-à-vis the bulk sample of GFCO scale with its reduced magnetization. This suggests that further improvements in the quality of the films are needed to improve their magnetization and hence their magnetocaloric properties, possibly making them useful for on-chip cooling in miniaturized devices.

Chirality and Magnetocaloricity in GdFeTeO6 as Compared to GdGaTeO6

“…This makes GdFeTeO 6 attractive for the working body of low-temperature magnetic refrigerator devices. With the intensification of research at helium temperatures, the problem of cooling the current leads of superconducting solenoids and reaching ultralow temperatures becomes increasingly urgent [32][33][34][35][36][37].…”

Magnetoelectric thin films by solution methods

“…Solution methods were used to synthesize stoichiometric coating solutions that were then spun-coated onto substrates as described elsewhere. [10][11][12][13] The crystal structure of the DyCrO 3 (DCO) film on 60 nm LaNiO 3 coated single crystalline (001) LaAlO 3 substrate as well as GdFe 0.5 Cr 0.5 O 3 (GFCO) and PbZr 0.52 Ti 0.48 O 3 :CoFe 2 O 4 (PZT:CFO) films on platinized silicon substrates were examined by X-ray powder diffractometer with Cu-Kα radiation (λ = 1.54 Å). The magnetic properties were measured using vibrating sample magnetometer (VSM) attached to an Evercool Physical Property Measurement System.…”

Quantitative Calculation of the Clustering Behavior of Fe‐Rich and Cr‐Rich REFepCr1−pO3 Crystals

“…The close ionic radius of Cr 3þ (0.615 Å) and Fe 3þ (0.645 Å) prevents it from forming a standard double perovskite structure. [10,21] The random arrangement of Fe 3þ or Cr 3þ ions leads to the appearance of Fe-and Cr-rich clustering (cluster state of Fe or Cr ions). [21,22] Additionally, the B-site ions produce an internal field acting on Gd 3þ ions in GdMO 3 , [23][24][25][26] which is formed jointly by the exchange field and the dipole field of the B-site ions.…”

“…As a result, it can be considered that T ¼ 11.97 K is the transition temperature that the ions' moment direction from order to disorder, which may correspond to the ordering temperature of Gd-Fe/Cr ferromagnetic exchange. [21,34,35] A second maximum, T ¼ 259.96 K, corresponds to the phase transition temperature T 2 of the superexchange interaction between Fe 3þ -O-Cr 3þ .…”

“…[ 10,21 ] The random arrangement of Fe 3+ or Cr 3+ ions leads to the appearance of Fe‐ and Cr‐rich clustering (cluster state of Fe or Cr ions). [ 21,22 ] Additionally, the B‐site ions produce an internal field acting on Gd 3+ ions in GdMO 3 , [ 23–26 ] which is formed jointly by the exchange field and the dipole field of the B‐site ions. [ 27 ] To the best of our knowledge, no study on the internal field of has been reported, nor has any theoretical analysis or calculation been performed on the cluster state of .…”