Growth and Characterization of High Entropy Perovskite (La_0.2Nd_0.2Gd_0.2Sm_0.2Y_0.2)MnO₃ Thin Films on Cubic and Orthorhombic Substrates

With the discovery of high entropy oxides in 2015 many different oxides have been synthesized using the high entropy strategy [1]. Since 2018 many different high entropy perovskites have been synthesized, some of them contain five elements on the A- or the B-site [2]. Some high entropy perovskites were synthesized with ten different elements, five on the A-site and five on the B-site [2]. Most of them were produced as polycrystalline powders, only a few oft them have been grown as thin film [2-5]. In the recent research, the focus has shifted to high entropy manganites-perovskites, because of their interesting magnetic properties, where the Mn-O-Mn exchange dominates the magnetic properties and the rare earth ion radii influences the strength of the exchange [3,4]. One high entropy manganite-perovskite is (La_0.2Nd_0.2Gd_0.2Sm_0.2Y_0.2)MnO₃which was previously produced as a powder [2].<br/>We have grown thin films of (La_0.2Nd_0.2Gd_0.2Sm_0.2Y_0.2)MnO₃ via pulsed laser deposition on three different substrates, one with a cubic structure SrTiO₃(001) and two with an orthorhombic structure, NdGaO₃(001), and YAlO₃(001). All films were subsequently annealed. X-ray diffraction data confirmed epitaxial growth of (La_0.2Nd_0.2Gd_0.2Sm_0.2Y_0.2)MnO₃on all substrates. Wide-range reciprocal space mapping and electron-backscattered diffraction revealed, that (La_0.2Nd_0.2Gd_0.2Sm_0.2Y_0.2)MnO₃ has three different crystal orientations on SrTiO₃ and two on NdGaO₃ and YAlO₃. On SrTiO₃ (La_0.2Nd_0.2Gd_0.2Sm_0.2Y_0.2)MnO₃grows in two different directions (001) and (110). The (001) orientated crystals are rotated by 45° with respect to the substrate, while the (110) crystals are aligned either to the substrate lattice or are also rotated by 45°. On NdGaO₃ we observed only (001) orientated crystals, but with two different in-plane orientations, either (001) or (110). On YAlO₃ two crystal orientations were observed (110) and (001), both are aligned to the substrate lattice. High-resolution transmission electron microscopy confirmed the perovskite structure and the epitaxial growth. All surfaces showed a grainy structure which was observed by atomic force microscopy. Zero-field-cooled and field-cooled measurements revealed a magnetic transition temperature around 38 K for (La_0.2Nd_0.2Gd_0.2Sm_0.2Y_0.2)MnO₃ grown on SrTiO₃, which is lower compared to most of the parent compounds. This is in good agreement with the magnetic measurements on corresponding powder. Below 25 K the rare earth elements couple antiferromagnetic to the manganese, which is indicated by a decrease of the magnetization in the field-cooled curve. All samples showed a small coercive field and a small remanent magnetization, which indicates a soft magnetic behaviour.<br/>[1] C. M. Rost, E. Sachet, T. Borman, A. Moballegh, E. C. Dickey, D. Hou, J. L. Jones, S. Curtarolo, and J.-P. Maria, Nature Communications <b>6</b>, 8485 (2015).<br/>[2] A. Sarkar, R. Djenadic, D. Wang, C. Hein, R. Kautenburger, O. Clemens, and H. Hahn, Journal of the European Ceramic Society <b>38</b>, 2318 (2018).<br/>[3] R. Das, S. Pal, S. Bhattacharya, S. Chowdhury, S. K. K., M. Vasundhara, A. Gayen, and M. M. Seikh, Physical Review Materials <b>7</b>, 024411 (2023).<br/>[4] A. Sarkar, R. Djenadic, D. Wang, C. Hein, R. Kautenburger, O. Clemens, and H. Hahn, Journal of the European Ceramic Society <b>38</b>, 2318 (2018).<br/>[5] A. R. Mazza, E. Skoropata, J. Lapano, J. Zhang, Y. Sharma, B. L. Musico, V. Keppens, Z. Gai, M. J. Brahlek, A. Moreo, D. A. Gilbert, E. Dagotto, and T. Z. Ward, Physical Review B <b>104</b>, 094204 (2021).