B. Becker

Tuning of magnetism in CePd2(Al1−xGax)3

Abstract Resistance, AC-susceptibility and specific heat measurements have been performed on CePd 2 (Al 1− x Ga x ) 3 with x ⩽ 0.2. We found that a small amount of Ga ( x ⩽ 0.02) substituted for Al in CePd 2 Al 3 leads to an increase of the antiferromagnetic transition temperature T N , with a maximum of T N = 2.84 K at x = 0.01. A larger amount of Ga results in a decrease of T N to 1.3 K at x = 0.2. From our measurements we conclude that the increase of T N is due to the reduction of Al site disorder, which has been proposed to play a major role in the magnetic behavior of CePd 2 Al 3 . The subsequent decrease of T N is caused by the larger disorder in the magnetic interactions and tuning of the RKKY-interaction.

Crystallographic disorder and magnetism in UPd2−xSn☆

The intermetallic compound UPd2Sn has been shown in previous investigations to crystallize in an orthorhombic structure (space group Pnma). No indications for magnetic or superconducting transitions were found. However, if the Pd content is reduced, then, similar to UNi2Sn, a structural transition occurs. We prepared UPd1.85Sn and found it to crystallize as a Heusler compound in the MnCu2Al-structure (space group Fm3m). Now the system undergoes a transition into a disordered magnetic state at Tmag ⋍ 28 K. Here, we present our measurements of the specific heat, susceptibility and muon relaxation of UPd1.85Sn, and discuss the nature of the magnetic state in relation to the crystallographic structure.

Magnetic behaviour of the new intermetallic compound Ce2Pd3Ge5

We have prepared a new Ce-intermetallic compound Ce2Pd3Ge5 crystallizing in the orthorhombic U2Co3Si5-structure, which is related to the CaBe2Ge2-lattice. Specific heat cp, resistivity ϱ and magnetic susceptibility χ show antiferromagnetic ordering below TN = 3.8 K. The specific heat cp, corrected for the lattice contributions, is described in terms of mean field theory. Also we derive the low-lying crystalline electric field levels. Our results are compared to those of CePd2Ge2.

Anomalous thermal, magnetic and transport properties of U2Rh3Si5☆

Previous studies have indicated U2Rh3Si5 to order antiferromagnetically below 25 K. In this work we investigate the nature of the transition in more detail on high-quality samples using heat capacity cp, magnetic susceptibility χ and electrical resistance ϱ. Below TN we observe an unusually large jump of 100 J/U mol K in cp, an anomalous decrease in the magnetic susceptibility and a huge drop (a factor of 65) in the electrical resistance. We propose that the dramatic antiferromagnetic ordering is caused by the formation of a two-level system with the corresponding opening of a spin-wave gap.

Non-collinear magnetic ordering in U2Rh3Si5☆

Abstract Neutron powder diffraction reveals a non-collinear antiferromagnetic arrangement of the eight uranium magnetic moments within the unit cell of U2Rh3Si5 below TN = 26 K. The μx component of the moments orders in ferromagnetic wavy sheets stacked antiferromagnetically along x, while μy exhibits a two-up, two-down configuration along y, else being stacked like μx. The magnetic structure is associated with the ordered moment μ = 1.81(5)μB at T = 8.5 K.

The magnetic structure of CePd2Ge2 and Ce2Pd3Ge5

Abstract The magnetic structures of CePd2Ge2 and Ce2Pd3Ge3 are determined by neutron powder diffraction. Both compounds show antiferromagnetic stacking of ferromagnetic planes of Ce moments, with moment values of 0.85μB (parallel to the stacking vector k ) and 1.25μB (perpendicular to k ), respectively.

UNi4B: ordered and disordered uranium moments

Abstract We demonstrate that the unusual magnetic properties of the hexagonal uranium compound UNi4B can be understood by the formation of a partially antiferromagnetic ordered state below TN = 20 K. Two dissimilar uranium moments exist due to the existence of a crystallographic superlattice. New low-temperature, high-field AC susceptibility and resistivity data down to 30 mK and 16 T suggest that the nonordering moments are gradually compensated as the temperature is lowered from TN to zero. These moments do not undergo another phase transition.

Metamagnetic transition and dHvA effect of U2Rh3Si5

Abstract We have successfully measured the dHvA frequency branches and effective masses in both the antiferromagnetic and field induced phases of U 2 Rh 3 Si 5 . The difference of the frequency branches between the phases are discussed in terms of the Fermi surface reconstruction due to the magnetic Brillouin zone. The values of the effective masses are between 5 m 0 and 8 m 0 except for the value of 0.5 m 0 measured for one particular frequency branch.