Abstract
In the field of nanoscale magnetocaloric materials, novel concepts like micro-refrigerators, thermal switches, microfluidic pumps, energy harvesting devices and biomedical applications have been proposed. However, reports on nanoscale (Mn,Fe)2(P,Si)-based materials, which are one of the most promising bulk materials for solid-state magnetic refrigeration, are rare. In this study we have synthesized (Mn,Fe)2(P,Si)-based nanoparticles, and systematically investigated the influence of crystallite size and microstructure on the giant magnetocaloric effect. The results show that the decreased saturation magnetization (Ms) is mainly attributed to the increased concentration of an atomically disordered shell, and with a decreased particle size, both the thermal hysteresis and Tc are reduced. In addition, we determined an optimal temperature window for annealing after synthesis of 300–600 °C and found that gaseous nitriding can enhance Ms from 120 to 148 Am2kg−1 and the magnetic entropy change (ΔSm) from 0.8 to 1.2 Jkg−1K−1 in a field change of Δμ0H = 1 T. This improvement can be attributed to the synergetic effect of annealing and nitration, which effectively removes part of the defects inside the particles. The produced superparamagnetic particles have been probed by high-resolution transmission electron microscopy, Mössbauer spectra and magnetic measurements. Our results provide important insight into the performance of giant magnetocaloric materials at the nanoscale.
Highlights
The magnetocaloric effect (MCE) describes the fundamental phenomenon that when a magnetic compound is exposed to a change in the applied magnetic field under adiabatic conditions it shows an increase or decrease in temperature
We have systematically studied the crystalline structure, thermodynamic, microstructure- and magnetic properties in (Mn,Fe)2(P,Si)-based nano magnetocaloric materials (MCMs) derived from bulk alloys by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), High-resolution transmission electron microscopy (HRTEM), SQUID and Mössbauer spectra
The change in crystallite size as a result of the high-energy ball milling (HEBM) process is found to be responsible for changes in TC, Thys, Stot and the magnetization
Summary
The magnetocaloric effect (MCE) describes the fundamental phenomenon that when a magnetic compound is exposed to a change in the applied magnetic field under adiabatic conditions it shows an increase or decrease in temperature This adiabatic temperature change Tad is associated with a transfer between magnetic and vibrational entropies. Since the seminal work on the discovery of GdSiGe-based MCMs by Pecharsky and coworkers in 1997 [1], a growing number of firstorder magnetic transition (FOMT) materials, which demonstrate a giant magnetocaloric effect (GMCE) have sprung up. This contrasts with most other magnetic materials that show a second order magnetic transition (SOMT).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
