Spin singlet formation in MgTi$_2$O$_4$: evidence of a helical dimerization pattern

Journal article

The transition metal spinel MgTi$_2$O$_4$ undergoes a metal-insulator transition on cooling below $T_{M-I} = 260$ K. A sharp reduction of the magnetic susceptibility below $T_{M-I}$ suggests the onset of a magnetic singlet state. Using high-resolution synchrotron and neutron powder diffraction, we have solved the low-temperature crystal structure of MgTi$_2$O$_4$, which is found to contain dimers with short Ti-Ti distances (the locations of the spin singlets) alternating with long bonds to form helices. Band structure calculations based on hybrid exchange density functional theory show that, at low temperatures, MgTi$_2$O$_4$ is an orbitally ordered band insulator.

Authors: Schmidt, M; Ii, W; Radaelli, P; Refson, K; Harrison, N

• Publication status: Published
• Journal: Physical Review Letters
• Volume: 92
• Issue: 5
• Pages: 564021-564024
• Publication date: 2003-08-06
• DOI: 10.1103/PhysRevLett.92.056402
• EISSN: 1079-7114
• ISSN: 0031-9007
• Language: English
• Keywords: cond-mat