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Unusual magnetic transition near metal-insulator transition and paramagnetic anomaly in VO2
Ist Teil von
Applied physics letters, 2017-04, Vol.110 (17)
Ort / Verlag
Melville: American Institute of Physics
Erscheinungsjahr
2017
Link zum Volltext
Quelle
AIP Journals Complete
Beschreibungen/Notizen
Experiments for vanadium dioxide show a magnetic transition characterized by a sharp variation in susceptibility associated with the metal-insulator transition at the temperature T
c. The sample is shown to be of Pauli paramagnetism above T
c but of anomalous paramagnetism below T
c. Considering co-contributions of Pauli paramagnetism of residual V4+ ions and Curie-like paramagnetism of V-V dimers, we propose a phenomenological expression for the temperature-dependent susceptibility below T
c, which yields an excellent agreement with the experimental data. The unusual temperature dependence of Curie-like susceptibility below T
c is explained to be due to the fact that every dimer is formed by spin paring at an angle θ close to 180° and hence has an effective spin expressed as
S
e
f
f
=
cos
(
θ
/
2
)
which decreases with lowering temperature. The observed metal-insulator and magnetic transitions are argued to be due to a transition from the high-temperature Pauli paramagnetic state of V4+ ions to the low-temperature dimerized state.