Large Coupled Magnetoresponses in EuNbO₂N

Abstract

We have explored a new strategy to discover materials with large resistive or capacitive responses to magnetic fields by synthesizing EuMO2N (M = Nb, Ta) perovskites that combine ferromagnetic order of S = 7/2 Eu2+ spins with possible off-center distortions of the d0 M5+ cations enhanced by covalent bonding to N. EuNbO2N shows colossal magnetoresistances at low temperatures and a giant magnetocapacitance. However, the latter response originates from a microstructural effect rather than an intrinsic multiferroism.

Large magnetoresistances and non-Ohmic conductivity in EuWO1+xN2−x

“…1͑a͔͒ but electron diffraction revealed a body-centered ͱ2a p ϫ ͱ 2a p ϫ 2a p supercell as was also observed in EuNbO 2 N. 3 The cubic lattice parameter a p increases slightly with the nitrogen deficiency x ͑a p = 3.9592͑4͒, 3.9622͑2͒ and 3.9675͑2͒ Å for x = 0.09, 0.17, and 0.25, respectively͒ due to lattice expansion from electron doping into the W:5d band ͑reduction of W 6+ to W 5+ ͒. The presence of Eu 2+ , as found in the EuMO 2 N ͑M =Nb,Ta͒ analogs, 3 is confirmed by the mean Eu-O/N distances of 2.80-2.81 Å in these pseudocubic structures ͑cf. 2.88 and 2.68 Å, respectively, predicted from ionic radii of Eu 2+ and Eu 3+ ͒ but full determinations of the superstructure will be needed to obtain accurate distances.…”

“…2 Many oxide families are known to have such properties, but the utility of an unexplored class of materials-europium͑II͒ oxynitride perovskites-was recently demonstrated as colossal negative magnetoresistances ͑MRs͒ were discovered at low temperatures. 3 The presence of nitride enables d 0 transition metals in high formal oxidation states to be stabilized, e.g., Nb, 3 Ta, 3,4 and W. 5 Nitrogen-deficiency leads to electrondoping of the transition metal d-bands and the carrier transport may be strongly coupled to the magnetization from the Eu 2+ S =7/ 2 core spins, leading to −MRϾ 99% for EuNbO 2+x N 1−x ͑MR= ͓ ͑H͒ − ͑0͔͒ / ͑0͒; is resistivity, measured in zero field and magnetic field H͒. Here we report the magnetotransport properties of the correspondingly electron-doped material EuWO 1+x N 2−x , in which large negative MRs and microstructurally induced nonohmicity are discovered.…”

“…Here we report the magnetotransport properties of the correspondingly electron-doped material EuWO 1+x N 2−x , in which large negative MRs and microstructurally induced nonohmicity are discovered. 3 and quenched to room temperature under ammonia. N contents were controlled by varying the flow rate between 200 and 270 cm 3 / min; x decreases as the flow rate increases.…”

Temperature and frequency dependent giant magnetodielectric coupling in DyMn0.33Fe0.67O3

“…20,21 This results in a negative MR and favours a positive MDC effect according to the Maxwell-Wagner model, similar to the positive MDC effect that occurs in EuNbO 2 N below the ferromagnetic transition temperature. 11 During our experiment measurement, dynamic frequency dependent resistances were obtained. Figure 5 presents the dynamic magnetoresistance in form of MR ¼ (R H ÀR H¼0 )/R H¼0 .…”

Structural and electronic structures of alkaline-earth transition metal oxynitride perovskites

“…It is why oxynitrides first reported by R. Marchand and co-workers 5) 19) and further widely investigated by several groups 20)30) have attracted great attention over the last years because of their potential applications not only as nontoxic pigments, 31) but also as dielectrics, 32) photocatalysts, 33) or colossal magnetoresistive materials. 22),34) For instance, BaTaO 2 N and SrTaO 2 N show high dielectric constants.…”