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

•Nanoparticles of LaFeO3 are successfully incorporated in MWCNTs.•Interestingly, phase transitions of LaFeO3-MWCNTs are observed in magnetic data.•Superparamagnetic relaxations of LFO in MWCNTs are found at and above ∼298 K.•Microwave absorption of LFO is highly enhanced in the composite of LFO-MWCNTs.

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 5 h 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 300 K down to 5 K, 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 ∼298 K and a spin-glass like behavior is found below ∼50 K. The electromagnetic wave absorbing properties in X and Ku bands of microwave regions (8-12 GHz and 12-18 GHz) measured by a vector network analyzer (VNA) confirm the significant enhancement of microwave absorption (RL ∼ −34.88 dB at 10.53 GHz for 1 mm thickness) of LFO in LFO-MWCNTs, which is quite interesting for such multiferroic system.