Enhanced microwave absorption and magnetic phase transitions of nanoparticles of multiferroic LaFeO3 incorporated in multiwalled carbon nanotubes (MWCNTs)

Abstract

Multiferroic nanoparticles of LaFeO3 (LFO) are prepared by a combination of sono-chemical and sol-gel auto combustion method. The as prepared sample is calcined at 500°C for 5h to get the desired crystallographic phase. To enhance the microwave absorption, nanoparticles of LFO are incorporated in the matrix of multi-walled carbon nanotubes (MWCNTs). Crystallographic phases of LFO and LFO-MWCNTs are confirmed by analyzing the X-ray diffractograms (XRD) using Rietveld method. The average size of nanoparticles, crystallographic phase, morphology, and incorporation of LFO nanoparticles in MWCNTs are also obtained by high-resolution transmission electron microscope (HRTEM). Micrographs, nanocrystalline fringe pattern and selected area electron diffraction pattern recorded during HRTEM observations confirmed the formation of the desired nanocomposite phase of LFO-MWCNTs. FTIR and Raman spectroscopy of LFO and LFO-MWCNTs are also recorded at room temperature (RT) which confirm the presence of the individual component in the nanocomposite sample. Hysteresis loops at different temperatures from 300K down to 5K, zero field cooled (ZFC) and field cooled (FC) magnetizations (M) as a function of temperature (T) of LFO-MWCNTs are recorded in SQUID magnetometer. Analysis of the observed magnetic data of LFO-MWCNTs suggests the presence of superparamagnetism above ∼298K and a spin-glass like behavior is found below ∼50K. The electromagnetic wave absorbing properties in X and Ku bands of microwave regions (8–12GHz and 12–18GHz) measured by a vector network analyzer (VNA) confirm the significant enhancement of microwave absorption (RL∼−34.88dB at 10.53GHz for 1mm thickness) of LFO in LFO-MWCNTs, which is quite interesting for such multiferroic system.