I. Magnetic, thermal and transport properties of YbCu${}_{5-x}$Zn${}_x$ alloys

Abstract

Within the family of cubic YbCu${}_4$X compounds ($X$ = Ni, Au and Zn), we have investigated the YbCu${}_{5-x}$Zn${}_x$ ($1\ge x\ge 0.7$) alloys by means of structural, magnetic, thermal and transport measurements. In the $\ddot{I}„1-$ YbCu${}_{5-x}$Zn${}_x$ (cubic AuBe${}_5$ type, $0.7\le x\le 1.5$) structural phase, Yb ion is in its Yb${}^{3+}$ magnetic configuration. However, by increasing Zn content the unit cell grows faster than a reference computed as a Cu by Zn atoms substitution, which indicates a shift of Yb ions towards the larger Yb${}^{2+}$ configuration. The magnetic behavior confirms such tendency with a clear decrease of the saturation magnetization and effective moment between $x=0.7$ and $x=1$. The specific heat at low temperature shows a logarithmic dependence characteristic for a non-fermi-liquid behavior. The characteristic energies of all studied parameters, including magneto resistivity, show notably low values as an indication that these alloys are close to a quantum critical point, which is approached from the non-magnetic side as the Zn content decreases.

6 pges, 6 figures