Magoda, Nyawasedza2023-11-142023-11-142022https://hdl.handle.net/10539/36975A dissertation submitted in fulfilment of the requirements for the degree of Master of Science to the Faculty of Science, University of the Witwatersrand, Johannesburg, 2022Iron-based novel materials have been generating enormous interest within the scientific community for a number of decades. The efforts on such materials have intensified after the discovery of the fascinating iron-pnictide superconductors. This intriguing discovery also provides added evidence to the significance of the structure-property relationship in establishing certain functional properties. This study is expected to lead to potential exciting and tuneable properties and might open a new direction for future investigations. The focus of this research is on the synthesis and physical property characterization of novel metallic compounds, RuFe3Si and RhFe3C. In this study, the compounds under investigation were synthesized using arc-melting, the properties of these materials were explored using various experimental techniques such as X-ray diffraction, Mössbauer Spectroscopy both performed at room temperature, magnetic susceptibility (𝜒), electrical resistivity (𝜌) and heat capacity (𝐶P) measurements. The results from wavelength-dispersive spectroscopy confirmed the ratio of each of the elements relative to each other of Ru:Fe:Si and Rh:Fe:C as 1:3:1. No impurities were detected for both compounds, but patches of unreacted carbon were identified in RhFe3C. Rietveld refinement of data collected from powder X-ray diffraction experiments established that both compounds crystallized in a cubic structure with 𝐹𝑚3̅𝑚 (225) space group symmetry. RuFe3Si is a single phase compound whereas RhFe3C had a secondary phase of unreacted carbon. Transmission Mössbauer spectroscopy performed at room temperature show that RuFe3Si has four different Fe sites within its structure where one of the sites has similar environment as -Fe. RhFe3C has three distinct Fe sites which are characterized by high magnetic internal fields. The (T) data of RuFe3Si measured at H = 1000 Oe between 2 to 950 K was analyzed and revealed a high transition temperature Tc = 773(5) K. Subsequent measurements performed at H = 100 Oe resulted in an increase in the magnitude of the Curie temperature, Tc = 873(3) K. The  1 (T) data was found to obey the Curie-Wiess law which resulted in 𝜃 = 828(17) K and an effective magnetic moment eff = 3.4(2) B/Fe . The positive sign of the Weiss temperature, 𝜃 demonstrates the presence of ferromagnetic (FM) interactions within the sample. Isothermal magnetization measurements as a function of the applied field were performed at various temperatures ranging from 2 K to 900 K for the compound RuFe3Si. A very narrow hysteresis loop is observed with small values of the coercive field and the remnant magnetization, which is indicative of a soft ferromagnet. The (T) data of RhFe3C measured at H = 1000 Oe between 300 to 1000 K showed no magnetic phase transitions within this temperature range. The 𝜌(𝑇) measurements performed on both samples revealed a positive temperature coefficient indicating that they are metallic. Experimental 𝐶𝑃 (𝑇) and 𝜌(𝑇) data for RuFe3Si was analyzed using Padé approximants representing the Debye model and Bloch-Grüneisen model which resulted in the following Debye temperatures 𝛩D (all T) = 430(1) K. and 𝛩𝑅 = 404(1)K. The 𝐶𝑉 (𝑇) data for RhFe3C was fitted with the Debye model with an added Einstein lattice contribution which resulted in 𝛩D(all T) = 784(14) and 𝛩E(all T) = 237(3) K . Fitting the low temperature data with a linear equation yielded a calculated value of 𝛩D = 453(2) K. The 𝜌(𝑇) data followed a quadratic trend which obeyed 𝜌(𝑇) = 𝜌0 + 𝐴𝑇 2 . This study confirmed the stoichiometric ratio of the constituent elements Ru:Fe:Si and Rh:Fe:C as 1:3:1 as expected. Secondary electron images collected over the polished surfaces of RuFe3Si revealed a homogeneous structure with no detectable impurities whereas in the case of RhFe3C traces of unreacted carbon along with the main phase were observed. Both are ferromagnetic compounds that crystalize within the 𝐹𝑚3̅𝑚 (225) space group symmetry and have a very high Curie ordering temperature.enMagnetic PropertiesElectronic PropertiesStructural PropertiesDissertation