Challenges in the Discovery and Characterization of Magnetic Intermetallics

The crystal growth and characterization of four families of compounds, LnFeSb3 (Ln = Pr, Nd, Sm, Gd, and Tb) and CeCo(Sb, Sn)3, Ln2Fe4Sb5 (Ln = La – Nd and Sm), LnCu2(Al,Si)5 (Ln = La and Ce), and Ln(Cu,Al,Ga)13 (Ln = La – Pr and Eu), are presented in this dissertation. Special emphasis is placed on describing their structure-magnetic properties correlations. Discoveries and studies of these systems were motivated by their structurally related predecessors, which are comprised of complex structural subunits and exhibit unusual physical properties. The magnetic behaviors exhibited by a selection of these intermetallics include the large magnetoresistances and varying degrees of magnetic anisotropy displayed by PrFeSb3 and NdFeSb3, spin glass behavior observed in the low temperature magnetic susceptibility measurements of La2Fe4Sb5, and the ferromagnetic and moderate magnetocaloric effects observed for Eu(Cu,Al,Ga)13 and Eu(Cu,Al)13. These materials are diverse and beautifully illustrate the complexity of the field of magnetism. Chapter 1 describes the motivations behind the explorations of the abovementioned phase spaces. X-ray and neutron scattering, magnetism, the magnetocaloric effect, and the origins of enhanced electron mass behavior will be reviewed. Additionally, this chapter serves to link these projects. Subsequent chapters provide an in-depth analysis of the structure-property correlations for each system which have been elucidated by their synthesis, structural determinations, and physical properties measurements.