Magnetic and orbital correlations in multiferroic CaMn7O12 probed by x-ray resonant elastic scattering

Abstract

The quadruple perovskite CaMn 7 O 12 is a topical multiferroic in which the hierarchy of electronic correlations driving structural distortions, modulated magnetism, and orbital order is not well known and may vary with temperature. X-ray resonant elastic scattering (XRES) provides a momentum-resolved tool to study these phenomena, even in very small single crystals, with valuable information encoded in its polarization and energy dependence. We present an application of this technique to CaMn 7 O 12. By polarization analysis, it is possible to distinguish superstructure reflections associated with magnetic order and orbital order. Given the high momentum resolution, we resolve a previously unknown splitting of an orbital-order superstructure peak, associated with a distinct locked-in phase at low temperatures. A second set of orbital-order superstructure peaks can then be interpreted as a second-harmonic orbital signal. Surprisingly, the intensities of the first-and secondharmonic orbital signal show disparate temperature and polarization dependence. This orbital reordering may be driven by an exchange mechanism that becomes dominant over the Jahn-Teller instability at low temperature.

Structural Stability and Properties of Marokite-Type γ-Mn3O4

“…Synthetic manganese oxides and manganese oxide minerals play an important role in different technological processes and applications. , For example, some of them are utilized as effective catalysts, − as supercapacitors, as ferroelectrics or multiferroics, − as elements in ion batteries, − as semiconductors, and for many other purposes. − In general, manganese oxides, including Mn-based perovskites, − are inexpensive and highly functional materials, which combine interesting electronic and magnetic properties and, therefore, have remained in the focus of recent investigations.…”

Synthesis of Ilmenite-type ε-Mn2O3 and Its Properties

“…Manganese oxides display a range of unique physical and chemical properties and play an important role in basic sciences and in numerous industrial processes and devices. For instance, they are promising materials for applications in diverse magnetic technologies, − for catalysis, , for supercapacitor electrodes, for lithium storage and alkaline battery applications, − and for other goals. − Various Mn-rich oxides, such as manganite perovskites, A 1– x B x MnO 3 , more complex quadruple perovskites, for example, AMn 7 O 12 , − and many others, − demonstrate interesting and often industry-relevant characteristics. Hence, the synthesis of novel, chemically simple, inexpensive, and functional manganese oxides could uncover yet unknown scientific and industrial potentials.…”