Polycrystalline samples of (Eu1−xYbx)2O3 (x = 0.0, 0.1, 0.2, 0.5, 0.8, 0.9 and 1.0) were synthesized by a sol–gel process. X‐ray diffraction data were collected and the crystal structures were refined by the Rietveld method. All samples are found to have the same crystal system and formed solid solutions over the whole range of x. The lattice parameters are found to vary linearly with the composition x. The cationic distribution over the two non‐equivalent sites 8b and 24d of the space group is found to be random in the range 0.0 < x≤ 0.5 and preferential in the range 0.5 < x≤ 1.0. Replacing Eu3+ and Yb3+ by each other introduces slight changes in the atomic coordinates. Crystallite size and microstrain analysis are performed on single and multiple orders for each sample using profile fitting and the Warren–Averbach method. The obtained values of microstrain are correlated with the distribution of the rare earth (RE) ions over the two cationic sites of the structure. The average crystallite size ranges from 35 to 96 nm and the mean‐square strain from 0.052 to 0.225 × 10−2.

It is known now that an increase in tumor temperature decreases the tumor resistance to chemo-and radiation therapies. Hyperthermia treatment of the tumor cells where damage to the healthy cells can be avoided is viable by using magnetic nanoparticles with controlled Curie temperatures. Nickel-Chromium (Ni 1-x Cr x ) particles with varying compositions have been investigated as thermoseeds for use in localized self controlled hyperthermia treatment of cancer. A series of Ni 1-x Cr x alloys, have been prepared to find the specific composition which has Curie temperature around 316-317 K. The samples were cast by arc melting technique, and were annealed at 850 o C for 5 hours in sealed quartz tubes. Magnetic properties of the samples were investigated, including Curie temperature, saturation magnetization and hysterisis using Superconducting Quantum Interference Device (SQUID) and Vibrating Sample Magnetometer (VSM). The Curie temperatures of the alloys were found to decrease almost linearly from 401 K to 289 K as the Cr concentration was increased from x = 4.54 wt % to x = 5.90 wt %. The results showed that Ni 1-x Cr x alloys might be good candidates for self regulating magnetic hyperthermia applications.

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