Magnetic phase diagram of pseudo-ternary solid solution URu1−xPdxGeURu1−xPdxGe

A systematic study of the solid solution URu1−xPdxGeURu1−xPdxGe by means of X-ray diffraction, dc-magnetization, specific heat and electrical resistivity measurements is presented. The investigated alloys (0.0≤x≤0.9)(0.0≤x≤0.9) crystallize in the orthorhombic TiNiSi-type structure with space group Pnma. The variation of the unit cell volume with Pd content x follows approximately Vegard׳s law, through the lattice parameters a, b and c exhibit a little anomaly around x  =0.35, 0.7 and 0.8, respectively. It is found that the magnetic ground state of URu1−xPdxGeURu1−xPdxGe strongly depends on Pd content. The compositions with x≤0.32x≤0.32 are nonmagnetic down to 0.4 K, while these in the concentration range 0.35≤x≤0.80.35≤x≤0.8 order antiferromagnetically. The Néel temperature TN is found to follow a relation TN∝(x−0.32)2/3TN∝(x−0.32)2/3 for the alloys x<0.45x<0.45 and to attain a maximum value of 32 K at x=0.8. The composition x=0.9 alike UPdGe manifests a complex magnetic order, probably undergoes two successive magnetic phase transitions: ferromagnetic-like at TC=33 K and unknown ground state characterized by an irreversible magnetization below TIR. The observed development of magnetism has been discussed in terms of changes in the degree of 5f electron localization as well as due to the competition between the Kondo and Ruderman–Kittel–Kausuya–Yosida interactions. Remarkably, in the compound x  =0.32 located at the nonmagnetic-magnetic border, we found a non-Fermi liquid behaviour reflected by the power-law temperature dependencies of magnetic susceptibility χ(T)∝T−0.48χ(T)∝T−0.48, specific heat Cp(T)∝−T and electrical resistivity ρ(T)∝T3/2ρ(T)∝T3/2. We compared the results with theoretical predictions for systems with spin fluctuations nearby antiferromagnetic quantum critical point.

Magnetic phase diagram of URu1−xPdxGeURu1−xPdxGe. Middle and bottom panel: concentration dependence of the exponent n   in the resistivity ATnATn term and the Sommerfeld ratio of URu1−xPdxGeURu1−xPdxGe at 2 K, respectively. Figure optionsDownload as PowerPoint slide