A study on the spectral, microstructural, and magnetic properties of Eu-Nd double-substituted Ba0.5Sr0.5Fe12O19 hexaferrites synthesized by an ultrasonic-assisted approach.

In this study, an examination on the spectral, microstructural, and magnetic characteristics of Eu-Nd double-substituted Ba0.5Sr0.5Fe12O19 hexaferrites (Ba0.5Sr0.5NdxEuxFe12-2xO19 (x = 0.00-0.05) HFs) fabricated by an ultrasonic-assisted approach has been presented. An UZ SONOPULS HD 2070 ultrasonic homogenizer with frequency of 20 kHz and power of 70 W was used. The chemical bonding, structure and the morphology of the products were evaluated by Fourier-Transform Infrared (FT-IR) Spectroscopy, XRD (X-ray diffraction), scanning and transmission electron microscopy and techniques. The textural properties of the prepared nanomaterials were examined by using the Brunauer-Emmett-Teller (BET) method. The magnetic properties were studied using a vibrating sample magnetometer (VSM) at room temperature (RT) and low temperature 10 K. The magnitudes of various magnetic parameters including Ms (saturation magnetization), Mr (remanence) and Hc (coercivity) were estimated and evaluated. The M-H loops revealed the hard ferrimagnetic nature for all products at both temperatures. The Ms and Mr values showed a decreasing tendency with increasing degree of Eu3+ and Nd3+ substitutions whereas Hc values displayed an increasing trend. At RT, Ms, Mr and Hc values lie in the ranges of 63.0-68.8 emu·g-1, 24.6-39.2 emu·g-1 and 2252.4-2782.1 Oe, respectively. At 10 K, the values of Ms, Mr and Hc lie between 87.5-97.1 emu·g-1, 33.5-40.1 emu·g-1 and 2060.6-2417.2 Oe, respectively. The observed magnetic properties make the prepared products promising candidates to be applied in the recording media.

Sonochemical synthesis of Dy3+ substituted Mn0.5Zn0.5Fe2-xO4 nanoparticles: Structural, magnetic and optical characterizations.

Mn0.5Zn0.5DyxFe2-xO4 (x ≤ 0.03) nanoparticles (NPs) were fabricated by using Ultrasonic irradiation using UZ SONOPULS HD 2070 ultrasonic homogenizer (frequency of 20 kHz and power of 70 W). Structural and morphological analyses were performed via XRD (X-ray powder diffractometer), TEM (Transmission electron microscopy) and SEM (Scanning electron microscopy). XRD presented the formation of Mn-Zn ferrite with average crystal size in 11 to 18 nm range. Direct optical energy band gaps (Eg) were specified applying diffuse reflectance investigations. Eg values are in a small band range of 1.61-1.67 eV. Low (10 K) and room temperature VSM data were recorded applying ±90 kOe external magnetic field. All samples exhibit superparamagnetic properties at RT. Magnetization parameters significantly increase due to coordination of Dy3+ rare earth ions. Magnetic moment per molecule (nB) increases from 0.952 µB to 1.137 µB and from 2.312 µB to 2.547 µB at RT and at 10 K data respectively. 10 K coercivity (Hc) values decrease from 260 Oe to 43 Oe. All samples have squareness ratios (SQR) of 0.231-0.400 range assigning the multi-domain structure at 10 K. ZFC-FC magnetization curves that were registered for two selected samples exhibit a divergence and a sharp drop below their Tpeak positions. This event is typically correlated to the collective freezing of system and spin-glass-like phase. Real part AC susceptibility data slightly shift toward high temperature regions with increasing frequencies. Critical Slowing Down (CSD) model explained the spin dynamics of interacting NPs consistently with literature and proved the spin-glass behavior of samples at low temperatures.

Sonochemical synthesis and physical properties of Co0.3Ni0.5Mn0.2EuxFe2-xO4 nano-spinel ferrites.

Nanoparticles (NPs) of composition Co0.3Ni0.5Mn0.2EuxFe2-xO4, where 0.00 ≤ x ≤ 0.10 (hereafter called CNMEuF) were synthesized by sonochemical approach using UZ SONOPULS HD 2070 ultrasonic homogenizer (frequency of 20 kHz and power of 70 W). As-synthesized samples were characterized thoroughly to determine the effects of europium ions (Eu3+) substitution on their structure, morphology and magnetic traits. Structural analyses of the synthesized NPs confirmed their high purity and crystalline cubic phases. Percent diffuse reflectance (%DR) data and Kubelka-Munk theory were exploited to evaluate the optical band gap energies of the studied CNMEuF NPs. Values of optical band gap energies obtained from the Tauc plots were observed in the range of 1.47-1.58 eV. The hysteresis loops (at room temperature and 10 K) of synthesized NPs were analyzed to determine their magnetic properties. These NPs disclosed superparamagnetic and hard ferrimagnetic character at room temperature and 10 K, respectively. With exception, the sample with x = 0.10 revealed soft ferrimagnetic behavior at 10 K. Eu3+ doping was shown to have significant influence on the structure and magnetic attributes of the proposed CNMEuF NPs. Values of various magnetic parameters of proposed compositions were reduced with the increase in Eu3+ dopant contents.