Abstract
Competing exchange interactions can produce complex magnetic states together with spin-induced electric polarizations. With competing interactions on alternating triangular and kagome layers, the swedenborgite CaBaCo4O7 may have one of the largest measured spin-induced polarizations of ∼1700 nC/cm2 below its ferrimagnetic transition temperature at 70 K. Upon rotating our sample about c=[0,0,1] while the magnetic field is fixed along [1,0,0], the threefold splitting of the spin-wave frequencies indicates that our sample is hexagonally twinned. Magnetization measurements then suggest that roughly 20% of the sample is in a domain with the a axis along [1,0,0] and that 80% of the sample is in one of two other domains with the a axis along either [-1/2,3/2,0] or [-1/2,-3/2,0]. Powder neutron-diffraction data, magnetization measurements, and terahertz (THz) absorption spectroscopy reveal that the complex spin order in each domain can be described as a triangular array of bitetrahedral c-axis chains ferrimagnetically coupled to each other in the ab plane. The electric-field dependence of bonds coupling those chains produces the large spin-induced polarization of CaBaCo4O7.
| Original language | English |
|---|---|
| Article number | 024423 |
| Journal | Physical Review B |
| Volume | 95 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 23 2017 |
Funding
Research sponsored by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division (RF), by the Hungarian Research Funds OTKA K 108918, OTKA PD 111756, and Bolyai 00565/14/11 (SB, VK, and IK), by the institutional research funding IUT23-3 of the Estonian Ministry of Education and Research and the European Regional Development Fund project TK134 (TR and UN), and by the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program) (YT, YT, and YT). We also acknowledge the support of the HFML-RU/FOM, member of the European Magnetic Field Laboratory (EMFL).