Neutron diffraction study of the magnetic structures of CeMn2Ge2 and CeMn2Si2

Abstract

We have performed high-resolution neutron powder diffraction measurements on CeMn2Si2 and CeMn2Ge2 at temperatures between 12 and 550 K. Our measurements indicate that at high temperatures both compounds are paramagnetic. Below TN=380 K CeMn2Si2 becomes a collinear AF, with a structure similar to that reported by Siek et al. in which the magnetic propagation vector is τ=(0 0 1). CeMn2Ge2, on the other hand, exhibits two different magnetic transitions. At TN≊415 K there is a transition to a collinear AF phase characterized by the commensurate propagation wave vector τ=(1 0 1). At TC≊318 K there is a transition to a conical structure with a ferromagnetic component along the c axis and a helical component in the ab plane. The helical component is characterized by the incommensurate propagation vector τ=(1 0 1−qz), where qz is temperature dependent.

Magnetic behavior in Ce1–xTbxMn2Si2 silicides by XRD, DSC and AC susceptibility measurements

“…Figure 2 shows the transformation during the heating temperature at a constant heating rate of 20 K/min. It is seen that for all the samples, an endothermic reaction takes place above room temperature, at which an antiferromagnetic alignment of Mn moments has been found by magnetic measurements for the samples with x = 0 and x = 1 [13,21]. Therefore, this transition temperature obtained from the DSC curve of the compounds, can be associated to the Néel temperature of antiferromagnetic alignment of the Mn sublattices for the samples with x = 0 and x = 1 and as well as for the other compounds.…”

Kondo effect in 3d-host ferromagnetic Sm1−xCexMn2Ge2

“…We find in Table 1 that the decreasing rates for T 1 and T 3 are, respectively, T 1 / x = 22 K and T 3 / x = 155 K. These observations can be explained within the following framework. Since Ce is non-magnetic down to 1.6 K [18,35,36] whereas Sm is ferromagnetically coupled with Mn-sublattice at temperatures below T 3 [21], the magnetic coupling is much stronger between Sm and Mn than between Ce and Mn. Thus, Ce for Sm substitution creates spin disorder on the ferromagnetically polarized Sm layers by diluting the Sm sublattice.…”

“…It is expected that Kondo-heavy-fermion behavior can be effectively affected by different types of magnetic fields. Although many studies have been carried out on Cebased Kondo-heavy-fermion materials in which the Ce ions are in non-magnetic host environments [7,10,11], very little work has been done on materials in which the Ce Kondo sites are embedded in robust internal host magnetic fields, such as the fields generated by the Mn-sublattice in the RMn 2 X 2 (R = rare-earth elements and X = Si, Ge) type materials [12][13][14][15][16][17][18][19][20].…”

The magnetic behaviours of R1−Gd Mn2Si2 (R: Ce and Pr) in weak magnetic field

“…The magnetic phase diagrams of Ce 1−x Gd x Mn 2 Si 2 and Pr 1−x Gd x Mn 2 Si 2 , shown in Figs. 5 and 6, are constructed by using the present magnetization data and the results of earlier neutron diffraction and magnetization measurement studies [1,[10][11][12][13][14]. For both systems, since all d a Mn-Mn values are smaller than 2.84 Å, the interlayer magnetic coupling between adjacent Mn planes is antiferromagnetic along the c-axis below T int er N and there is no in-plane Mn moment component.…”

“…Similarly, the Mn moment alignment in CeMn 2 Si 2 is also antiparallel along the c-axis below T int er N = 465 K down to low temperature. There is no magnetic alignment in the Ce sublattice in the whole temperature range [14].…”