Abstract
We demonstrate how chemical pressure affects the structural and electronic phase transitions of the quadruple perovskite CaMn7O12 by Sr doping, a compound that exhibits a charge-ordering transition above room temperature making it a candidate for oxide electronics. We have synthesized Ca1−xSrxMn7O12 (0 ≤ x ≤ 0.6) thin films by oxide molecular beam epitaxy on (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates. The substitution of Sr for Ca results in a linear expansion of the lattice, as revealed by X-ray diffraction. Temperature-dependent resistivity and X-ray diffraction measurements are used to demonstrate that the coupled charge-ordering and structural phase transitions can be tuned with Sr doping. An increase in Sr concentration acts to decrease the phase transition temperature (T*) from 426 K at x = 0 to 385 K at x = 0.6. The presence of a tunable electronic phase transition, above room temperature, points to the potential applicability of Ca1−xSrxMn7O12 in sensors or oxide electronics, for example, via charge doping.
Highlights
There is growing interest in quadruple perovskites, (AA 3)B4O12,1–3 due to the wide range of physical properties found in this material class
An orbital-ordering transition is observed at ∼250 K (T OO) through scattering and Raman spectroscopy measurements.[17,18]
Similar transitions are observed in bulk SrMn7O12, with little change in the magnetic transition temperatures but a decrease of ∼60 K reported in T *
Summary
There is growing interest in quadruple perovskites, (AA 3)B4O12,1–3 due to the wide range of physical properties found in this material class. (Received 3 July 2017; accepted 23 August 2017; published online 18 September 2017)
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