Spin-orbit coupling driven magnetism in transition metal oxides
In the last decade many Sd comp
unds having for instance Iridium, have been reported which went
against the expectations of a wide-band metallic state . This insulating
state was shown to be an outcome of increased spin-orbit coupling (SO
0.5 ev) in these elements . lridates
therefore, with several competing energy scales: the Hubbard
Hunds exchange JH, SOC, crystal field (CF
and electron hopping energy t, are predicted to show a rich phase diagram of
exciting physical properties [1 ].
A unique situation develops if the Ir ions are in 5+ (Sd") oxidati 。 n state, where ideally str 。 ng SOC should lead to a non-magnetic 1=0 ground state. Our results on a 6H hexag 。 nal comp 。 und Ba3Znlr209 with lr5+ ions and strong SOC arrives very cl 。 se to the J = 0 state but each Ir ions still possess a weak moment . The spins within structural lr209 dimers are expected to form a spin- 。 rbit singlet state (SOS) with no resultant moment, but substantial frustration arising from inter-dimer exchange interactions induce quantum fluctuati 。 ns in these possible SOS states favoring a spin- 。 rbital liquid phase down t 。 at least 100 mK.
Unable to obtain J = 0 state in the comp 。 unds having Ir p9 dimers, we decided t 。 see the effect of separating the Ir ions by non-magnetic ions in double perovskite Ba2Ylr06. Although we observe the J = 0 state to be largely separated from the higher magnetic states in Resonant Inelastic X:-Ray Scattering experiments, which could be explained using an atomic model, magnetic moments were still 。 bserved from magnetic measurements suggesting that a minute amount of hopping still exists between the Ir ions. These m 。 ments that are generated, also do no order till 60 mK .
A question thus remains, w 。 uld it be ever possible to observe atomic like spin-orbit coupled states in a solid?
Hos t : Prof. Changyoung Kim