Manganites with double perovskite structure are being attractive because of their interesting magnetoelectric and dielectric responses. Particularly, colossal dielectric constant (CDC) behavior has been observed in La 2 CoMnO 6 (LCMO), at radio frequencies and room temperature. In this paper, we employed infrared-reflectivity spectroscopy onto a LCMO ceramic obtained through a modified Pechini's method to determine the phonon contribution to the intrinsic dielectric response of the system and to investigate the CDC origin. The analysis of the main polar modes and of the obtained phonon parameters show that CDC effect of LCMO is of pure extrinsic origin. In addition, we have estimated the dielectric constant and quality factor of the material in microwave region, ' s 16 and Q u × f 124 THz, which shows that LCMO is appropriate for applications into microwave devices and circuitry.

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...

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