Magnetic Moments and Ordered States in Pyrochlore Iridates Nd₂Ir₂O₇ and Sm₂Ir₂O₇ Studied by Muon-Spin Relaxation

Approaching the quantum critical point in a highly correlated all-in–all-out antiferromagnet

“…The projected phase boundary TN(P) is consistent with the three observed phase points (Fig. 4c), identified through magnetization M(T) at ambient P, the temperature dependence of I(006)(T) at P=6.26 GPa, and the pressure dependence of I(006)(P) at T=4 K. At ambient pressure, Sm moments in Sm2Ir2O7 have an estimated size of 0.1 µB/Sm 3+ , and order at T~10K [27]. Both are much smaller than the Ir moment size of 0.3 µB/Ir 4+ and the ordering temperature TN~110 K [27].…”

“…4c), identified through magnetization M(T) at ambient P, the temperature dependence of I(006)(T) at P=6.26 GPa, and the pressure dependence of I(006)(P) at T=4 K. At ambient pressure, Sm moments in Sm2Ir2O7 have an estimated size of 0.1 µB/Sm 3+ , and order at T~10K [27]. Both are much smaller than the Ir moment size of 0.3 µB/Ir 4+ and the ordering temperature TN~110 K [27]. By comparison to several pyrochlore iridates with large A-site moments (2.6-9 µB per Nd 3+ , Er 3+ , or Tb 3+ ) [28,29], the magnetic coupling strength between Sm 3+ 4f moments is likely much below 0.1 meV [28], and Sm 3+ ordering would rely on the assistance of the Ir 4+ molecular field, making it parasitic to the Ir AIAO order.…”

Strongly-coupled quantum critical point in an all-in-all-out antiferromagnet

“…4c), identified through magnetization M(T) at ambient P, the temperature dependence of I(006)(T) at P=6. 26 GPa, and the pressure dependence of I(006)(P) at T=4 K. At ambient pressure, Sm moments in Sm2Ir2O7 have an estimated size of 0.1 µB/Sm 3+ , and order at T~10K [27]. Both are much smaller than the Ir moment size of 0.3 µB/Ir 4+ and the ordering temperature TN~110 K [27].…”

Monopole-limited nucleation of magnetism in Eu2Ir2O7

“…Pyrochlore iridium oxides, with characteristic chemical formula R 2 Ir 2 O 7 , R being a rare-earth ion, host a wide variety of exotic electronic phases arising from the combined effect of the spin-orbit interaction, Coulombic correlations and the peculiar geometrical properties of the lattice [1,2] making them candidate materials for the realization of electronic states with nontrivial topological properties [3][4][5][6][7][8][9]. Particular interest has been devoted to the metal-insulator transition developing for R = Eu, Sm, and Nd, where a low-temperature magnetic insulating phase evolves into a nonmagnetic metallic state above a critical temperature T N [10][11][12][13][14][15][16][17][18][19][20][21][22]. Interestingly, T N shows a marked decrease upon increasing the average ionic size at the R site towards the limit of Pr 2 Ir 2 O 7 , a metallic spin liquid, which remains nonmagnetic down to the lowest accessible temperatures [23][24][25].…”