Understanding the influence of critical parameters such as temperature (tann), time (t), and pressure (P) on the functional properties of compounds is essential for both fundamental and applied science. This knowledge is crucial for comprehending physical and chemical processes and for developing new eco-friendly refrigeration technologies based on these materials. In this context, manganese-containing perovskite oxide nanoparticles have been synthesized, and their functional properties have been extensively studied in relation to the interconnected characteristics of tann, t, and P. By varying the temperature (tann), nanoparticles of different sizes, ranging from 20 to 70 nm, were obtained. The structural properties of these nanoparticles changed significantly after a long waiting time of t = 3 years. Observations showed that the particle size (D) increased, the bandwidth (W) widened, the microstrains (ε) increased, and the dislocation density (δ) decreased. Notably, the most significant changes in structural properties occurred in the smallest nanoparticles. Magnetic phase diagrams indicate that the phase transition temperatures rise with increasing tann, t, and P. Specifically, the smallest and most magnetically inhomogeneous nanoparticles exhibited the greatest change in Curie temperature (TC) over time (t), while the largest and most magnetically uniform nanoparticles showed the most significant variation in response to pressure (P). After a duration of t = 3 years, the largest nanoparticles demonstrated the most stable phase transition temperatures, with improved magnetocaloric parameters near room temperature. Among the parameters studied, time (t) exerted the greatest influence on the change of ΔTC/ΔP regarding pressure, following the order: t > tann > P. These three characteristics—tann, t, and P—serve as powerful tools for precisely tuning magnetic phase transition temperatures and the magnetocaloric effect of perovskite oxide nanoparticles, enabling the design of new materials with desired functional properties.

Associate Professor Mykyta Liedienov graduated from Donetsk National University in 2014 and obtained a Master’s degree diploma with honors in Radiophysics and Electronics. From 2014 to 2017, he was a post-graduate student of the Phase Transformations department at Donetsk Physical and Technical Institute, named after O.O. Galkin of the National Academy of Sciences of Ukraine. He obtained a Candidate of Physical and Mathematical Sciences in Solid State Physics (equivalent to a Ph.D.) at B. I. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine (Kharkiv, Ukraine) in 2018. His dissertation studied magnetotransport and dielectric properties of non-stoichiometric Bi-containing rare-earth manganites with a perovskite structure. From 2018 till 2023, he started to work on a post-doctoral position at Jilin University. In 2023, he obtained an Associate Professor position at the same university. To date, the total number of his publications is more than 100, among which are 35 articles, 2 patents, and 75 abstracts at international conferences. His publication citations are 687, and his h-index is 18. He participated in 7 scientific projects, two of which he headed. He is also a Reviewer of the 16 Journals. He has many diplomas, awards, and certificates at international scientific conferences, as well as has received several scholarships from the National Academy of Sciences of Ukraine for young scientists. The main direction of his scientific work is the study of the structural, microstructural, magnetic, resistance, magnetoresistance, baroresistance, ferroelectric, magnetoresonance, magnetothermal, magnetocaloric, and barocaloric properties of nanosized, bulk, and composite perovskites under extreme conditions: pressure, temperature, magnetic, and electric fields.