| AVS 66th International Symposium & Exhibition | |
| Magnetic Interfaces and Nanostructures Division | Wednesday Sessions |
| Session MI+2D-WeA |
| Session: | Emerging Multifunctional Magnetic Materials II |
| Presenter: | Navid Mottaghi, West Virginia University |
| Authors: | N.M. Mottaghi, West Virginia University M.S.S. Seehra, West Virginia University C.-Y. Huang, West Virginia University S. Kumari, West Virginia University S. Yousefi Sarraf, West Virginia University G. Cabrera, West Virginia University G. Bhandari, West Virginia University R.B. Trappen, West Virginia University M.B. Holcomb, West Virginia University |
| Correspondent: | Click to Email |
La0.7Sr0.3MnO3 (LSMO) with Curie temperature TC ≈ 370 K is one of the manganites which has been of interest for applications in magnetic memory devices and spintronics.1 The magnetic properties of LSMO thin films are also known to depend on the thickness of the films.2 Recent magnetic investigations of a 7.6 nm LSMO film grown by pulsed laser deposition (PLD) showed it to have a TC ≈ 290 K with a magnetic dead layer d ≈ 1.4 nm which demonstrated behavior consistent with containing superparamagnetic (SPM) spin clusters with blocking temperature TB ≈ 240 K.3,4 Here we report magnetocaloric properties of this LSMO thin film for temperatures T ≤TC in magnetic fields H up to 4 kOe. In particular, magnetic entropy SM(T, H) is evaluated from the isothermal plots of magnetization (M) vs. H at different temperatures (Fig. 1) using the Eq. ∆SM (T,H)= ∑i [(Mi+1 (Ti+1, H) - Mi (Ti, H))/(Ti+1-Ti)] ∆H. The H-dependence of ∆SM (T,H) is analyzed using the relation (-∆SM)=aHn, where a is a constant and n =2/3 is expected at T = TC.5 Our fit of the data to this Eq. for several T ≤ TC in Fig. 2 shows n ~ 1 for T < TC with the magnitude of n increasing for T > TC. This deviation of n from n = 2/3 is likely due to presence of SPM spin clusters in the dead layer for T < TC. The larger magnitudes of n for T > TC is due to the Curie-Weiss variation of the magnetization in this regime.5
References
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2 M. Huijben, L.W. Martin, Y.-H. Chu, M.B. Holcomb, P. Yu, G. Rijnders, D.H.A. Blank, and R. Ramesh, Phys. Rev. B 78, 94413 (2008).
3 N. Mottaghi, R.B. Trappen, S. Kumari, C.Y. Huang, S. Yousefi, G.B. Cabrera, M. Aziziha, A. Haertter, M.B. Johnson, M.S. Seehra, and M.B. Holcomb, J. Phys. Condens. Matter 30, 405804 (2018).
4 N. Mottaghi, M.S. Seehra, R. Trappen, S. Kumari, C.-Y. Huang, S. Yousefi, G.B. Cabrera, A.H. Romero, and M.B. Holcomb, AIP Adv. 8, 056319 (2018).
5 M. Pękała, J. Appl. Phys. 108, 113913 (2010).