Abstract
Multiferroic Ba2CuGe2O7 was anticipated as a potential member of the exciting group of materials hosting a skyrmion or vortex lattice because of its profound Dzyaloshinskii–Moriya interaction (DMI) and the absence of single ion anisotropy (SIA). This phase, however, could not be evidenced and instead, it exhibits a complex incommensurate antiferromagnetic (AFM) cycloidal structure. Its sister compound Ba2MnGe2O7, in contrast, is characterized by a relatively strong in-plane exchange interaction that competes with a non-vanishing SIA and the weak DMI, resulting in a quasi-two-dimensional commensurate AFM structure. Considering this versatility in the magnetic interactions, a mixed solid solution of Cu and Mn in Ba2Cu1−xMnxGe2O7 can hold an interesting playground for its interactive DMI and SIA depending on the mixed spin states of the transition metal ions towards the skyrmion physics. Here, we present a detailed study of the micro- and macroscopic spin structure of the Ba2Cu1−xMnxGe2O7 solid solution series using high-resolution neutron powder diffraction techniques. We have developed a remarkably rich magnetic phase diagram as a function of the applied magnetic field and x, which consists of two end-line phases separated by a potentially quantum-critical phase at x = 0.57. An AFM conical structure at zero magnetic field is demonstrated to persist up to x = 0.50. Our results provide crucial information on the spin structure and magnetic properties, which are necessary for the general understanding and theoretical developments on multiferroicity in the frame of skyrmion type or frustrated AFM lattice where DMI and SIA play an important role.
| Original language | English |
|---|---|
| Article number | 58 |
| Journal | npj Quantum Materials |
| Volume | 9 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2024 |
Funding
M.A. and V.H. conceived and supervised the project. The HC measurements were carried out by P.\u010C., N.K., and H.T. The magnetic susceptibility measurements were conducted by H.T. in discussion with S.N. The neutron powder diffraction experiments were performed by H.T. and V.H., supported by Q.Z. at POWGEN (SNS) and by J.L. at BT-1 (NIST). H.T. V.H., M.A., and R.D. contributed to the analysis and interpretation of the data. The single- and polycrystalline samples have been grown by V.G., supervised by R.F., and prepared for the measurements by H.T. The paper is written by R.D. and H.T. and all co-authors made comments on the paper. Specific heat measurements were performed in MGML (mgml.eu), which is supported within the program of Czech Research Infrastructures (project no. LM2023065). A portion of this research used resources at the SNS, a DOE Office of Science User Facility operated by the ORNL. The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology.