Magnetizing a material without applying an external magnetic field is proposed by researchers at São Paulo State College (UNESP), Brazil, in an article printed within the journal Scientific Experiences, the place they element the experimental strategy used to attain this objective.
The examine was half of the Ph.D. analysis pursued by Lucas Squillante below the supervision of Mariano de Souza, a professor at UNESP’s Division of Physics in Rio Claro. Contributions have been additionally made by Isys Mello, one other Ph.D. candidate supervised by Souza, and Antonio Seridonio, a professor at UNESP’s Division of Physics and Chemistry in Ilha Solteira. The group was supported by FAPESP.
“Very briefly put, magnetization happens when a salt is compressed adiabatically, without exchanging warmth with the external environment,” Souza advised. “Compression raises the temperature of the salt and on the similar time rearranges its particles’ spins. As a consequence, the overall entropy of the system stays fixed and the system stays magnetized on the finish of the method.”
To assist perceive the phenomenon, it’s price recalling the fundamentals of spin and entropy.
Spin is a quantum property that makes elementary particles (quarks, electrons, photons, and so on.), compound particles (protons, neutrons, mesons, and so on.) and even atoms and molecules behave like tiny magnets, pointing north or south—up spin and down spin—when submitted to a magnetic field.
“Paramagnetic supplies like aluminum, which is a steel, are magnetized solely when an external magnetic field is utilized. Ferromagnetic supplies, together with iron, could show finite magnetization even within the absence of an utilized magnetic field as a result of they’ve magnetic domains,” Souza defined.
Entropy is mainly a measure of accessible configurations or states of the system. The higher the quantity of accessible states, the higher the entropy. Austrian physicist Ludwig Boltzmann (1844-1906), utilizing a statistical strategy, related the entropy of a system, which is a macroscopic magnitude, with the quantity of doable microscopic configurations that represent its macrostate. “Within the case of a paramagnetic material, entropy embodies a distribution of possibilities that describes the quantity of up spins or down spins within the particles it comprises,” Souza stated.
Within the just lately printed examine, a paramagnetic salt was compressed in a single route. “Software of uniaxial stress reduces the quantity of the salt. As a result of the method is carried out without any trade of warmth with the atmosphere, compression produces an adiabatic rise within the temperature of the material. An increase in temperature means a rise in entropy. To maintain complete entropy within the system fixed, there should be a element of native discount in entropy that offsets the rise in temperature. As a consequence, the spins are likely to align, resulting in magnetization of the system,” Souza stated.
The overall entropy of the system stays fixed, and adiabatic compression ends in magnetization. “Experimentally, adiabatic compression is achieved when the pattern is compressed for much less time than is required for thermal leisure—the everyday time taken by the system to trade warmth with the atmosphere,” Souza stated.
The researchers additionally propose that the adiabatic rise in temperature might be used to analyze different interacting techniques, corresponding to Bose-Einstein condensates in magnetic insulators, and dipolar spin-ice techniques.
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Extra info:
Lucas Squillante et al, Elastocaloric-effect-induced adiabatic magnetization in paramagnetic salts because of the mutual interactions, Scientific Experiences (2021). DOI: 10.1038/s41598-021-88778-4
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