Intrinsic dielectric properties of magnetodielectric La2CoMnO6

Abstract

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.

High-temperature structural phase transition and infrared dielectric features of La2CoMnO6

“…Figure 1 shows the room temperature IR reflectivity spectrum of the partially ordered LCMO sample obtained at 1100 o C. The spectrum can be fitted according to the four-parameter semi-quantum model proposed by Gervais and Piriou 37 for describing the dielectric function. In this model, the complex dielectric function 𝜀(𝜔) is expressed in terms of the IR-active phonons 31,32,34 as…”

“…Recently, we have investigated the intrinsic dielectric constant in LCMO by means of their IR-active optical phonons, which shed light on the discussion about the colossal dielectric constant in this material. In short, it was undoubtedly showed that the CDC has an extrinsic origin 32 , since the intrinsic dielectric constant remains well behaved (s < 15), even for fully ordered samples 29,32 . Moreover, since all the crystal structures presented by LCMO are centrosymmetric, the IR and Raman-active optical phonons are complementary.…”

Calculation of the optical phonons in ordered Ba2MgWO6 perovskite using short‐range force field model

“…The W atom also plays a role in this infrared active mode, since the force constants K 3 (bond W–O) e H 2 (angle Ba–O–W) have contributions to PED of 24% and 26%, respectively. Indeed, reported investigations on the infrared reflectivity spectra of double perovskites have demonstrated that Last‐type modes have the greatest dielectric strength and then play a pivotal role in the static dielectric constant at infrared frequencies . The F 1u mode located at 658 cm −1 (expt.…”

“…Such classical methodology is based on lattice dynamics calculations (LDC) within Wilson's GF‐method for solution of the secular equation, representing a rapid and efficient method to assign the vibrational spectra of an arbitrary crystalline structure by generating the complete set of eigenvalues and their respective eigenvectors . Indeed, the normal coordinate analysis have been successfully employed to assign the optical modes in several ordered double perovskites, including cubic Ba 2 B'WO 6 and monoclinic Sr 2 B'UO 6 (where B′ = Ni, Co), and monoclinic manganite with chemical formula RE 2 CoMnO 6 (where RE = La, Gd). Here, using our results on lattice dynamical study of Ba 2 MgWO 6 , we briefly discussed possible effects of disorder on the phonon spectra of cubic double perovskites.…”

Electrical transport properties and enhanced magnetoresistance effect in double perovskite La2–xCaxCoMnO6 (0 ≤ x ≤ 0.5)

“…Double perovskite La 2 CoMnO 6 , one type of A 2 BB'O 6 , has been extensively studied due to its rich physical properties . The strong ferromagnetic (FM) super‐exchange interactions between Co and Mn ions lead to the high FM behavior of this material with a Curie temperature ( T C ) as high as 220 K .…”