Pages: 95-102

Authors: Božidar Dj. Cekić, Ana B. Umićević, Valentin N. Ivanovski,
Rongwei Hu, Cedomir Petrovic, Bohumil David, Tanja Barudžija

Abstract

The perturbed angular correlation method was employed to study the temperature dependence of electric field gradients at the ¹⁸¹Ta probe in the polycrystalline Hf₂Ni₇ compound. The temperature evolution of the sample content was measured using high-temperature X-ray diffraction. To check the magnetic order of the sample, magnetization measurements and additional perturbed angular correlation measurements with externally applied magnetic field were performed. All obtained spectra showed no evidence of magnetic order of the Hf₂Ni₇ phase. Within the experimental resolution of the apparatus, the measured electric field gradients at ¹⁸¹Ta probe for the two inequivalent ¹⁸¹Hf /¹⁸¹Ta sites in the Hf₂Ni₇ compound appeared as one in the range of 78-944 K. A single quadrupole interaction implies that the electric field gradients at the two Hf sites must be quite similar. At 293 K, the measured quadrupole interaction parameters are ν_q= 433(1) MHz and η = 0.300(4). An increase of the quadrupole frequency and a gradual rising of the asymmetry parameter were observed with increasing temperature. The high-temperature X-ray diffraction indicated a build up of HfO₂ above 693 K.

Key words: intermetallics, hyperfine interactions, perturbed angular correlation, magnetization, X-ray diffraction

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