Site Preference and Possible Coexistence of Antiferromagnetic Order and Magnetic Frustration in (Co _{1– x} Mg _x ) ₁₀ Ge ₃ O ₁₆ (0 ≤ x ≤ 30%)

High Resolution Image Download MS PowerPoint Slide 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 nonmagnetic Mg 2+ into a magnetically complicated system, Co 10 Ge 3 O 16, which contains three frustrated sublattices of Co 2+, e.g., triangular Co1, Kagome Co2, and Co3 sublattices. By growing crystals for (Co 1– x Mg x ) 10 Ge 3 O 16 (0 < x ≤ 30%), we observed obvious site preference of Mg 2+ on Co1 and Co3 sites over the Co2 site. Powder X-ray diffraction (XRD) patterns confirm the high purity of the samples and indicate a systematic peak shift, consistent with the loading compositions. Although previously investigated, the magnetic structure and expected magnetic frustration in this system have not been 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 Mg 2+ doping, while two new magnetic features emerge at a high Mg 2+ level. Moreover, the structural phase transition from the high-temperature R 3̅ m to the low-temperature C 2/ 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, (Co 0.7 Mg 0.3 ) 10 Ge 3 O 16, 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 Mg 2+ -induced spin-glass state. This study provides more insights into the complex magnetism in Co 10 Ge 3 O 16 by using the nonmagnetic Mg 2+ as a probe. However, detailed magnetic structure requires further efforts for growing large single crystals.