This study shows that adiabatic compression can produce the phenomenon without the need for heat exchange with the environment. Credit: Geek3/Wikimedia Commons - commons.wikimedia.org/wiki/File:VFPt_bar-magnet-forces.svgResearchers at So Paulo State University (UNESP), Brazil have proposed a method of magnetizing a material without using an external magnetic field. They published their findings in Scientific Reports.This study was part of Lucas Squillante's Ph.D. research under Mariano de Souza (a professor at UNESP’s Department of Physics, Rio Claro). Isys Molly, another Ph.D. candidate, was also supervised by Souza and Antonio Seridonio who is a professor at UNESP’s Department of Physics and Chemistry, Ilha Solteira. FAPESP supported the group.Souza explained that magnetization is when salt is compressed adiabatically without exchanging heat. "Compression increases the salt's temperature and rearranges its spins. The system's total entropy remains constant, and it remains magnetized at its end.It is worthwhile to review the basics of spin, entropy and other concepts in order to understand the phenomenon.Spin is a quantum property which makes elementary particles (quarks electrons photons etc. ), compound particles (protons, neutrons, mesons, etc.) Even atoms and molecules can behave as tiny magnets by pointing north or southup and down spin when placed in a magnetic field."Paramagnetic materials such as aluminum, which are metals, can only be magnetized when an external magnetic force is applied. Souza explained that ferromagnetic materials such as iron may exhibit finite magnetization even without an applied magnetic field. This is because they have magnetic domains."Entropy simply refers to the number of configurations that are possible or states in a system. Entropy is a measure of the system's accessibility. The more states there are, the higher the entropy. Ludwig Boltzmann (1844-1906), an Austrian physicist, used a statistical approach to determine the entropy. This is the macroscopic magnitude of the system. It also includes the possible microscopic configurations of its macrostate. Souza stated that entropy is a distribution or probabilities that describes how many up spins and down spins the material contains.A study published recently showed that a paramagnetic sodium was compressed in one direction. The salt's volume is reduced by the application of uniaxial strain. The process of compression is performed without heat exchange with the environment. This causes an adiabatic increase in the material's temperature. An increase in temperature is a sign of an increase in entropy. To maintain the equilibrium of total entropy, the system must have a local component of reduced entropy to offset the temperature rise. Souza explained that the spins align and magnetize the system as a result.Magnetization is achieved when the total entropy remains constant. Souza explained that adiabatic compression can be achieved by compressing the sample for less time than it takes for thermal relaxation, the time required for the system to exchange heat and the environment.Researchers also suggest that the adiabatic temperature rise could be used for investigating other interacting systems such as BoseEinstein condensates within magnetic insulators and dipolar spin-ice system.Continue reading Concepts from Physics explain the importance of quarantine in controlling spread of COVID-19More information: Lucas Squillante et al, Elastocaloric-effect-induced adiabatic magnetization in paramagnetic salts due to the mutual interactions, Scientific Reports (2021). Journal information: Scientific Reports Lucas Squillante et al, Elastocaloric-effect-induced adiabatic magnetization in paramagnetic salts due to the mutual interactions,(2021). DOI: 10.1038/s41598-021-88778-4
