The magnetic, transport, and magnetotransport properties of ${\mathrm{Mn}}_{3+x}{\mathrm{Sn}}_{1-x}\mathrm{C}$ $(0⩽x⩽0.4)$ and ${\mathrm{Mn}}_3{\mathrm{Zn}}_y{\mathrm{Sn}}_{1-y}\mathrm{C}$ $(0⩽y⩽0.9)$ compounds are investigated systematically. For ${\mathrm{Mn}}_{3+x}{\mathrm{Sn}}_{1-x}\mathrm{C}$, a sharp rise in temperature dependence of resistivity is observed for $x⩽0.1$, accompanied by a magnetic phase transition from a paramagnetic state to a complicated spin arrangement composed of antiferromagnetic and ferromagnetic sublattices. A different behavior appears in the resistivity of ${\mathrm{Mn}}_{3.2}{\mathrm{Sn}}_{0.8}\mathrm{C}$, which decreases monotonically with decreasing temperature. A partial Zn substitution for Sn in ${\mathrm{Mn}}_3\mathrm{Sn}\mathrm{C}$ leads to dramatic changes of magnetic and transport properties. As the temperature decreases, a magnetic transition from the ferromagnetic (or ferrimagnetic) to antiferromagnetic state occurs at about 170 and $142\mathrm{K}$ for ${\mathrm{Mn}}_3{\mathrm{Zn}}_{0.4}{\mathrm{Sn}}_{0.6}\mathrm{C}$ and ${\mathrm{Mn}}_3{\mathrm{Zn}}_{0.5}{\mathrm{Sn}}_{0.5}\mathrm{C}$ compounds, respectively, which strongly affects their transport properties. A significant magnetoresistance as large as 34% is observed for ${\mathrm{Mn}}_3{\mathrm{Zn}}_{0.5}{\mathrm{Sn}}_{0.5}\mathrm{C}$ at $95\mathrm{K}$, in accordance with a field-induced metamagnetic transition. The origin of the magnetoresistance effect is discussed in terms of the reconstruction of the Fermi surface.

• Received 26 April 2004

DOI:https://doi.org/10.1103/PhysRevB.72.024411