Spin-phonon coupling in Gd(Co1/2Mn1/2)O3 perovskite

Abstract

We have investigated the temperature-dependent Raman-active phonons and the magnetic properties of Gd(Co1/2Mn1/2)O3 perovskite ceramics in the temperature range from 40 K to 300 K. The samples crystallized in an orthorhombic distorted simple perovskite, whose symmetry belongs to the space group. The data reveals spin-phonon coupling near the ferromagnetic transition occurring * Corresponding Author: C. W. A Paschoal: e-mail: paschoal@ufma.br; Tel +55 98 3301 8291 2 at around 120 K. The correlation of the Raman and magnetization data suggests that the structural order influences the magnitude of the spin-phonon coupling. 3Rare-earth manganite perovskites present a very rich interplay between electric and magnetic properties that has been demonstrated in a plethora of phenomena observed in either bulk, powders or strained thin films. For instance, we can cite giant and colossal magnetoresistances observed in LaMnO3-based perovskites [1], occurrence of multiferroic behavior [2,3] and the discovery of the strong magnetodielectric coupling in ordered La(Ni1/2Mn1/2)O3 perovskite (usually written as La2NiMnO6, hereafter LNMO) [4]. The exploration of the chemical substitutions in the B-site has concentrated many efforts in REMnO3 (RE = rare earth) perovskites, since the choice of magnetic and ionic radius of the RE and substitute B cations, drives the magnetism, the ferroelectricity, and their coupling [5][6][7][8][9][10][11][12].The ferroic and multiferroic properties depend on the unit cell topology (cations' size, angles and distances), therefore investigations of the spin-phonon coupling of manganites are of crucial interest and a convenient tool to study the magnetically induced ferroelectric systems [13]. Indeed, there is a vast literature on the investigation of spin-phonon coupling in magnetoelectric materials using both Raman and infrared spectroscopies comprising both simple and double perovskites [7,12,[14][15][16]. Sample preparation, including the exploitation of epitaxy-induced strains, impacts the multiferroic properties and raises interesting differences between specimens prepared following different routes but with identical chemical composition. A paradigmatic example is the Co-substituted ordered manganite La2CoMnO6 (LCMO) that shows spin-phonon coupling in thin-films, while the phonon modes remain insensitive to magnetic order in bulk samples [17]. The conclusive explanation of this particular difference remains unraveled and calls for further investigations to the entire family, including ordered (conventionally typed RE2CoMnO6) and disordered (conventionally typed RE(Co1/2Mn1/2O3) compounds.. In this Letter, we have investigated the spin-phonon 4 coupling in the Gd(Co1/2Mn1/2)O3 (GCMO) perovskite using temperature-dependent Raman spectroscopy, which has been an important tool to investigate order, magnetic transitions, and spin-phonon coupling in perovskites [12,15,[18][19][20][21][22].Polycrystalline samples of GCMO were synthesized by polymeric precursor method [23] using cobalt acetate t...

Spin–phonon coupling in monoclinic BiCrO3

“…So far, a general trending on the phonon renormalization due to a spin-phonon coupling has been reported in a large number of compounds and, usually, antiferromagnetic systems present a hardening effect on phonon frequencies, 42,43 whereas ferromagnetic materials show a softening effect. 44,45 Nevertheless, the λ factor has a complex character that depends on the atomic motions involved in the phonon mode, and, for this reason, some compounds seem to be beyond this rule.…”

Spin-phonon and magnetostriction phenomena in CaMn7O12 helimagnet probed by Raman spectroscopy

“…Thus, both phenomena should imply in anomalies in the phonon spectra parameters. Raman scattering is a powerful probe to observe the coupling between magnetic ordering and lattice [11][12][13][14][15][16][17] . However, recent investigations on lowtemperature Raman-active phonon properties in CMO have not detected any anomalies in the magnetic transitions in CMO 18 .…”

Temperature-dependent structural and magnetic properties of R2MMnO6 double perovskites (R = Dy, Gd; M = Ni, Co)

“…[24][25][26]. In Gd 2 CoMnO 6 , entropy changes related both to the ferrimagnetic ordering of Co/Mn cations near 110 K and at lower temperatures (T ~ 10 K) due to the presence of large Gd magnetic moments and their coupling to the 3d moments were recently reported [11,12,27,28].…”