Site Preference and Possible Coexistence of Antiferromagnetic Order and Magnetic Frustration in (Co1-xMgx)10Ge3O16 (0 <= x <= 30%)

TL;DR

This study investigates how Mg2+ doping affects magnetic order and frustration in Co10Ge3O16, revealing site preferences, suppression of certain magnetic transitions, and the emergence of new magnetic features, advancing understanding of complex magnetism.

Contribution

It provides new insights into site-specific magnetic behavior and frustration in doped Co10Ge3O16 using systematic Mg2+ doping and various characterization techniques.

Findings

Mg2+ prefers Co1 and Co3 sites over Co2.

Doping suppresses high-temperature antiferromagnetic transition.

Emergence of spin-glass state at high Mg2+ levels.

Abstract

Geometrically frustrated magnetism has attracted tremendous attention while chemical doping has been utilized as an important tool to probe frustrated magnetism in various systems. Here we perform a systematic study by doping non-magnetic Mg2+ into a magnetically complicated system, Co10Ge3O16, which contains three frustrated sublattices of Co2+, e.g., triangular Co1, Kagome Co2 and Co3 sublattices. By growing crystals for (Co1-xMgx)10Ge3O16 (0 < x <= 30%), we observed obvious site preference of Mg2+ on Co1 and Co3 sites over the Co2 site. Powder X-ray diffraction (XRD) patterns confirm the high purity of the samples and indicate systematic peak shift, consistent with the loading compositions. Although previously investigated, the magnetic structure and expected magnetic frustration in this system are not fully uncovered. Our temperature-dependent magnetic susceptibility measurements suggest that the high-temperature magnetostructural phase transition with antiferromagnetic ordering and a low-temperature broad peak are suppressed with Mg2+ doping, while two new magnetic features emerge at high Mg2+ level. Moreover, the structural phase transition from high-temperature R-3m to low-temperature C2/m space group is absent at the antiferromagnetic ordering temperature, as confirmed by single-crystal XRD. By analyzing the heat capacity and neutron powder diffraction results of the highest doped sample, (Co0.7Mg0.3)10Ge3O16, we speculate that the Co1 site is responsible for the long-range antiferromagnetic ordering, while the other two sites are short-range correlated in addition to a Mg2+-induced spin-glass state. This study provides more insights into the complex magnetism in Co10Ge3O16 by using the non-magnetic Mg2+ as a probe. However, detailed magnetic structure requires further efforts on growing large single crystals.