Er Sites Research Articles

Field-induced magnetic transition in CrCo 3

The action of a magnetic field on a single crystal of the compound ErCo 3 has been investigated by both magnetization and neutron diffraction measurements. ErCo 3 is ferrimagnetic with an easy magnetization axis parallel to the c axis of the crystal. When the field is applied perpendicular to the c axis a transition occurs: the moment of one of the two Er sites remains nearly oriented along the c axis while this of the other Er site rotates through an angle of 55°. From the value of the threshold field, the difference between the anisotropy energies of the two sites has been evaluated.

Magnetic and thermal studies on ErCo2–ErAl2

Details of the magnetization behavior of the pseudobinary system ErCo2–ErAl2 at temperatures from 1.6 to about 70 K are presented and compared with previous neutron diffraction experiments. ErCo2 shows a first-order phase transition at 33 K from ferrimagnetic order to paramagnetism. Replacement of Co by Al destroys this unusual feature and initially results in enhanced magnetic exchange with increasing ordering temperatures, although the Co moment is rapidly decreasing due to electron transfer. The moment on Co sites is completely quenched beyond 30 mole% ErAl2. Disordered magnetic components on Er sites which develop in the pseudobinary region and have been identified with neutrons can be partly forced into the field direction, but the saturation values are limited by the anisotropy. The origin of disorder is discussed as being either a consequence of the disorder on crystallographic sites or of the changing valence electron concentration. Differential thermal analysis shows only the onset of magnetic ordering and no signs of subsequent magnetic transitions at lower temperatures (down to 4.2 K) for materials with only partial magnetic order.

Structures cristallines des composés intermétalliques erbium-cobalt de compositions intermédiaires entre ErCo 5 et Er 2Co 17

The intermetallic compounds ErCo x have been investigated by X-ray diffraction method in the composition range between Er 2Co 07 ( x = 3.5) and Er 2Co 17 ( x = 8.5). For the quenched samples with 5.5 < x <5.75 the crystal structure is found to be of the CaZn 5 type, part of the Er sites of the ideal structure being occupied at random by a pair of Co atoms. For x > 5.75 two phases are observed; the CaZn 5-type phase coexists with another structure having an ordered arrangement of the Co pairs at the Er sites. At x = 8.5 the latter gives the Er 2Co 17 structure. In the annealed samples a mixture of the Er 2Co 7 and Er 2Co 17 phases can be observed. The variation of the lattice parameters with the concentration has also been studied.