Magnetic Properties and Magnetocaloric Effect of Polycrystalline and Nano-Manganites Pr0.65Sr(0.35−x)CaxMnO3 (x ≤ 0.3)

Abstract

Here we report investigations of bulk and nano-sized Pr0.65Sr(0.35⁻x)CaxMnO3 compounds (x ≤ 0.3). Solid-state reaction was implemented for polycrystalline compounds and a modified sol–gel method was used for nanocrystalline compounds. X-ray diffraction disclosed diminishing cell volume with increasing Ca substitution in Pbnm space group for all samples. Optical microscopy was used for bulk surface morphology and transmission electron microscopy was utilized for nano-sized samples. Iodometric titration showed oxygen deficiency for bulk compounds and oxygen excess for nano-sized particles. Measurements of resistivity of bulk samples revealed features at temperatures associated with grain boundary condition and with ferromagnetic (FM)/paramagnetic (PM) transition. All samples exhibited negative magnetoresistivity. Magnetic critical behavior analysis suggested the polycrystalline samples are governed by a tricritical mean field model while nanocrystalline samples are governed by a mean field model. Curie temperatures values lower with increasing Ca substitution from 295 K for the parent compound to 201 K for x = 0.2. Bulk compounds exhibit high entropy change, with the highest value of 9.21 J/kgK for x = 0.2. Magnetocaloric effect and the possibility of tuning the Curie temperature by Ca substitution of Sr make the investigated bulk polycrystalline compounds promising for application in magnetic refrigeration. Nano-sized samples possess wider effective entropy change temperature (ΔTfwhm) and lower entropy changes of around 4 J/kgK which, however, puts in doubt their straightforward potential for applications as magnetocaloric materials.

A Short Review on the Evolution of Magnetocaloric La(Fe,Si)13 and Its Fabrication through Melt Spinning

“…23,56 So far as we are aware, La(Fe,Si) 13 alloys cannot be cast in large quantities. Melt spinning has been used to refine the primary Fe phase, while powder metallurgy (HDSH) 69 has been used to insert hydrogen atoms into alloys, although these processes produce a powder and/or ribbon rather than a solid material.…”

“…The findings demonstrate that grinding and particle size selection can boost the proportion of the fcc-La­(Fe,Si) 13 and, in turn, the magnetocaloric effect reaction relative to the original bulk sample. , So far as we are aware, La­(Fe,Si) 13 alloys cannot be cast in large quantities. Melt spinning has been used to refine the primary Fe phase, while powder metallurgy (HDSH) has been used to insert hydrogen atoms into alloys, although these processes produce a powder and/or ribbon rather than a solid material.…”

“…The La(Fe,Si) 13 alloy composition formed by arc melting is compared and detailed in the Table 2. According to Table 2, the magnetic field strength that is applied during the measurement of the change in magnetic entropy 69 is exactly proportional to each other. 70 The data that are presented in Table 2.…”

Charge-ordering breakdown dynamics and ferromagnetic resonance studies of B-site Cu diluted Pr1‒x Sr x MnO3

“…Nevertheless, in S55C10, the substitution of Cu on the B site replaces the Mn 3+ ions and increases the Mn 4+ /Mn 3+ ratio. Thus, competition between the two ordered parameters associated with the COAFM and DE ferromagnetism goes in favor of the latter leading to a resultant FiM alignment of the unequal magnetic spins present in the system [23,24]. Besides, a drastic increase in bifurcation between the χ FC and χ ZFC curves below T irr (∼250 K) signifies an additional role of magnetocrystalline anisotropy (MCA) in the Cu-doped system in comparison with the pristine S55 system.…”

“…Our choice of this parent compound is guided by the phase diagram of PSMO, which exhibits intriguing behavior around x ∼ 0.50, where properties affected by the OO/CO phenomena show a high sensitivity to minute variations in x. While Pr 0.5 Sr 0.5 MnO 3 has been extensively studied in previous literature [23][24][25], Pr 0.45 Sr 0.55 MnO 3 has received less attention. However, considering the sensitivity of the properties to x in this region, this specific composition is of subsequent interest.…”