Nanocomposites and nanomaterials

Magnetocaloric effect in nanoparticles of non-stoichiometric manganite
Wei Ziyu1, Liedienov N.A.1,2, Pashchenko A.V.1,2,3, Li Quanjun1
1 State Key Laboratory of Superhard Materials, International Centre of Future Science, Jilin University. Qianjin Street, Changchun-130012, China. 
E-mail: nikita.ledenev.ssp@gmail.com
2 Donetsk Institute for Physics and Engineering named after O. O. Galkin, NASU. Prospect Nauki,46, Kyiv-03028, Ukraine
3 Institute of Magnetism, NAS of Ukraine and MES of Ukraine. Vernadsky Blvd., 36, Kyiv-03142, Ukraine.

Manganite has become a promising candidate material for magnetic refrigerants because it exhibits a considerable magnetocaloric effect near room temperature [1]. Many researches are devoted to controlling the magnetic entropy change in manganites through various chemical and physical methods [2].
Here, we have synthesized the non-stoichiometric La0.8-xK0.2Mn1+xO3 (0 ≤ x ≤ 0.2) spherical-like nanocrystalline samples with an average particle size of about 40 nm. The magnetic properties and magnetocaloric effect of these compounds were studied as a function of manganese doping level. The temperature dependences of magnetization show that excess manganese doping can significantly improve the ferromagnetic nature and change the phase transition temperature slightly. The composition with the highest entropy change ΔSMmax = –3.629 J / (kg∙K) under 3 T at TC = 332 K is the La0.8-xK0.2Mn1+xO3 with x = 0.05. The obtained results demonstrate possible ways for controlling magnetic and magnetocaloric properties of the La0.8-xK0.2Mn1+xO3 manganites using excess manganese doping and creating cation vacancies on A-sites of the perovskite structure.

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2.	Phan M. -H., Yu S. -C. Review of the magnetocaloric effect in manganite materials // J Magn Magn Mater.-2007.-308.-P. 325-340.