Tunable Electromagnetic Properties of Epitaxial Mo(d²)-Doped SrRu(d⁴)O₃ Thin Films

4<i>d</i> transition metal oxides (TMOs) offer various intriguing physical behaviors resulting from the strong interplay among charge, spin, lattice, and orbital degrees of freedom. Their electronic structure is influenced not only by the on-site Coulomb interaction (<i>U</i>) and spin-orbit coupling (SOC) but also by Hund’s coupling (<i>J_H</i>). There have been several studies conducted to construct the correlated electronic phase diagram by varying the degree of those interaction parameters. One of the renowned 4<i>d</i> TMOs is the ferromagnetic SrRuO₃(SRO) with 4<i>d</i>⁴ configuration having abundant electronic states including non-Fermi liquid and Weyl semimetal states. The intrinsic SOC coupled with its ferromagnetism is important for the emergence of the Dzyaloshinskii – Moriya interaction beneficial for the observation of exotic quantum phenomena, such as the skyrmion formation and resultant topological Hall effect [1, 2]. On the other hand, SrMoO₃ (SMO) with 4<i>d</i>² configuration is the other reported metallic 4<i>d</i> TMO influenced by Hund’s coupling. However, its electronic transport mechanism is less understood compared to SRO despite its extremely small room-<i>T</i> resistivity with Fermi-liquid behavior [3]. Different from SRO, SMO is reported to have <i>T</i>-independent magnetic susceptibility exhibiting Pauli paramagnetic behavior.<br/>Previously, several attempts have been made to dope SRO thin films with 3<i>d</i> and 5<i>d</i> TM ions through Ru-site chemical substitution which results in the suppression of the ferromagnetism and emergence of metal-insulator transition in the electronic transport. In this study, we investigated the effect of Mo(4<i>d</i>²)-doping on SRO thin films by manipulating the degree of electronic and magnetic correlations through chemical substitution. We grew the epitaxially stabilized SrRu_1-<i>x</i>Mo<i>_x</i>O₃ (SRMO, <i>x</i> = 0 – 0.5) thin films using pulsed laser epitaxy by alternately ablating two targets, SRO and SMO. The Mo concentration was selectively controlled by adjusting the laser pulse numbers according to the deposition rate of each target on (001) SrTiO₃ substrates. The high quality of the resulting SRMO thin films has been confirmed by using x-ray diffraction accompanied by a systematic lattice compression per the increase in the Mo concentration. The modification of the complex 4<i>d</i>⁴ electronic structure by the 4<i>d</i>²-doping is apparent in the hybridization between Ru 4<i>d</i> and O 2<i>p</i> orbitals, inducing systematic changes in the electric and magnetic properties of SRMO epitaxial thin film. Our results present further insights into understanding the systematic changes in the electromagnetic properties of epitaxial SRMO thin films useful for spintronic device applications.<br/><br/>References:<br/>[1] Meng, Keng-Yuan <i>et al.</i>, <i>Nano Lett.</i> 2019, 19, 5, 3169–3175.<br/>[2] Wang, C. A. <i>et al.</i>, <i>Adv. Electron. Mater.</i> 2020, 6, 2000184.<br/>[3] Prasetiyawati, R. D. <i>et al.</i>, Curr. Appl. Phys. 2023, 53, 110.