Emerging spin–phonon coupling through cross-talk of two magnetic sublattices

Abstract

Many material properties such as superconductivity, magnetoresistance or magnetoelectricity emerge from the non-linear interactions of spins and lattice/phonons. Hence, an in-depth understanding of spin–phonon coupling is at the heart of these properties. While most examples deal with one magnetic lattice only, the simultaneous presence of multiple magnetic orderings yield potentially unknown properties. We demonstrate a strong spin–phonon coupling in SmFeO3 that emerges from the interaction of both, iron and samarium spins. We probe this coupling as a remarkably large shift of phonon frequencies and the appearance of new phonons. The spin–phonon coupling is absent for the magnetic ordering of iron alone but emerges with the additional ordering of the samarium spins. Intriguingly, this ordering is not spontaneous but induced by the iron magnetism. Our findings show an emergent phenomenon from the non-linear interaction by multiple orders, which do not need to occur spontaneously. This allows for a conceptually different approach in the search for yet unknown properties.

EXAFS evidence for the spin–phonon coupling in the monoclinic PrNiO3 nickelate perovskite

“…39 A recent paper on RNiO 3 nickelates (R = Y, Er, Ho, Dy, Sm, Nd) revealed phonon anomalies around both magnetic ordering and insulator-metal transition temperatures by means of Raman spectroscopy. 7 In all of the papers mentioned above and others cited elsewhere, [40][41][42] the phonon anomaly is in general explained by considering the contribution of four physical effects: (i) lattice expansion/contraction described by the volume change and Gru ¨neisen parameter; (ii) intrinsic anharmonicity of the phonon mode according to the Balkanski's model; 43 (iii) phonon renormalization due to the electronic states at the spin ordering temperature; and (iv) modulation of the exchange integral as a consequence of the spin-phonon coupling. The latter effect may be stronger when the magnetic ordering appears concomitantly with the insulator-metal transition, being the case of both PrNiO 3 and NaOsO 3 .…”

Magnetostructural coupling in RFeO3 (R = Nd, Tb, Eu and Gd)

“…This implies the specific role of this mode in the spin–phonon coupling of the studied compounds, even at the spin-reorientation of NdFeO 3 . The shifts ranging from 1 to 3 cm −1 , with the expected magnitude for spin–phonon coupling effects 37 – 40 , would correspond to octahedra rotation changes, estimated to be between 0.05° and 0.15°, arising from the magnetostructural coupling. The Raman mode wavenumber shift are positive, except for EuFeO 3 .…”

“…We now aim at understanding the cross-talk of the magnetic R –Fe interaction with the phonon lattice, as recently observed in SmFeO 3 40 . To do so, we address the out-of-phase R -oscillations modes, shown in Fig.…”

Field-Tuning Mechanisms of Spin Switching and Spin Reorientation Transition in Praseodymium–Erbium Orthoferrite Single Crystals

“…Recently, the net magnetic moment of PrFeO 3 in the low-temperature region under very low field 5 Oe was reported to shift from the c -axis to the a -axis with increasing temperature, indicating a Γ 4 –Γ 2 SR transition in a PrFeO 3 single crystal . In addition to PrFeO 3 , it is known for most RFeO 3 families; such SR transitions with Γ 4 states in the high-temperature region and Γ 2 states in the low-temperature region have been reported for ErFeO 3 , − YbFeO 3 , SmFeO 3 , , etc. In the RFeO 3 family, SR transitions or the induced new magnetic phase transitions in RFeO 3 are often regulated through the rare-earth site or transition metal-site ionic doping.…”

“…Rare-earth orthoferrites (RFeO 3 , R = rare-earth elements), as a family of canted antiferromagnetic materials, have many attractive and rich magnetic properties, such as magneto-optical effect, multiferroics, spin–phonon coupling, ultrafast spin switching, and spin reorientation (SR) transition, and thus have attracted significant interest from researchers in different fields. − The presence of Dzyaloshinskii–Moriya (DM) interactions makes RFeO 3 exhibit a canted antiferromagnetic ordering in terms of the magnetic structure, and its weak ferromagnetic moment is stabilized in a specific crystal axis direction at a certain temperature . The RFeO 3 space group with a distorted perovskite structure is D 2h 16 - Pbnm , containing two magnetic systems of an R 3+ sublattice and an Fe 3+ sublattice, exhibiting a magnetic structure with canted antiferromagnetic coupling with Néel temperature of the Fe 3+ sublattice in the range of 600–750 K .…”