Magnetic order in the pyrochlore iridate Nd2Ir2O7probed by muon spin relaxation

Abstract

Muon-spin relaxation results on the pyrochlore iridate Nd 2 Ir 2 O 7 are reported. Spontaneous coherent muonspin precession below the metal-insulator transition (MIT) temperature of about 33 K is observed, indicating the appearance of a long-ranged magnetic ordering of Ir 4+ moments. With further decrease in temperature, the internal field at the muon site increases again below about 9 K. The second increase of internal field suggests the ordering of Nd 3+ moments, which is consistent with a previous neutron experiment. Our results suggest that the MIT and magnetic ordering of Ir 4+ moments have a close relationship and that the large spin-orbit coupling of Ir 5d electrons plays a key role for both MIT and the mechanism of the magnetic ordering in pyrochlore iridates in the insulting ground state.

Direct determination of the spin structure ofNd2Ir2O7by means of neutron diffraction

“…The Nd moment and the net moment of its six nearest neighboring Ir ions are aligned parallel (ferromagnetic) . Our results are consistent with our findings in µSR data [11] which indicate that the Ir 4+ moments are almost saturated below 20 K while the strongest increase of the ordered moment of the Nd 3+ ions appears below about 9 K.…”

“…Subsequent studies of Nd 2 Ir 2 O 7 by means of µSR measurements yield controversial results. One µSR study supports the AIAO magnetic structure on both sublattices [11] whereas the other one indicates that the Nd sublattice can not order in an AIAO magnetic structure since the calculated internal field at the muon site is much larger than the experimental value with the proposed magnetic structure [21].Here, we report the first successful determination of the magnetic structure of a pyrochlore iridate by means of neutron diffraction. Using an optimized sample geometry and a strong neutron flux we were able to solve the magnetic structure of Nd 2 Ir 2 O 7 including the spin structure of the Ir sublattice.…”

“…No thermal hysteresis effect can be observed at T MI (T N ), thus, indicating a second order transition [9]. At T N , magnetization, µSR and resonant X-ray scattering experiments suggest an ordering of the Ir 4+ moments [9,[11][12][13][14]. At lower temperatures, the d − f interaction may induce the magnetic ordering at the R site (also depending on the single-ion anisotropy at the R site [15] [17,18].…”

Enhanced weak ferromagnetism and conductivity in hole-doped pyrochlore iridateY2Ir2O7

“…When the A 3+ ion is magnetic, the possible f-d exchange interaction 14 between the Ir 4+ and A 3+ leads to even more complex magnetic structures. 9,17,23,25,37,38 Therefore, to clarify the fundamental magnetic properties associated with the iridium tetrahedral network, it is desired to choose the compounds with non-magnetic A-site ions, e.g. Eu 3+ , 18,19 Bi 3+ , [26][27][28][29] and Y 3+ .…”

Colossal enhancement of electrical conductivity in Y2Ir2O7nanoparticles

“…In general, the magnetic ground state emerges due to the interplay between Heisenberg-type antiferromagnetic interaction, Dzyaloshinskii-Moriya interaction emerging due to strong spin-orbit coupling and single-ion anisotropy [1,13,14]. If R 3+ is also magnetic, more complex magnetic ground state could be obtained [17,16,18,15,19]. Fortunately, the problem simplifies considerably for Y 2 Ir 2 O 7 since it has nonmagnetic Y 3+ ions residing at Rsite.…”