Neutron scattering study of magnetic order in single-crystallineCeCuAl3

Incommensurate antiferromagnetic order in CePtAl$_3$

“…This simple type of magnetic order is quite different from the modulated types reported for tetragonal CeCuAl 3 [12] and CeAuAl 3 [13] (see Tab. I), but it bears strong resemblance to the ferromagnetic ordering in the orthorhombic CeAgAl 3 .…”

“…The exact determination of magnetic structure is flawed by the fact that only (h 0 l) reflections were measured, and cannot be distinguished between a tetragonal multi-k model and twinned, orthorhombic single-k model. Interestingly, the model of the magnetic structure of the tetragonal CeCuAl 3 proposed by [12], is of orthorhombic symmetry, since the magnetic moments are arranged along the (1 1 0) diagonal, clearly favoured over the model with moments pointing along the (1 1 0) diagonal, which is equivalent to (1 1 0) assuming tetragonal symmetry. In fact, just as in case of CePtAl 3 , constraining the model to tetragonal symmetry leads to a multi-k structure with a complex arrangement of magnetic moments, discussed in more detail in Supplementary Materials ?…”

“…As such, the simplistic arguments based on interatomic distances don't predict well the type of magnetism exhibited by these compounds. Klicpera et al [12] suggest a diagram that relates the magnetic modulation vector of CeT X 3 compounds based on unit cell volume and NN Ce distances. It predicts that both CePtAl 3 and CePdAl 3 should possess k = (0 0 k z ) modulation vector, which is clearly not the case for CePtAl 3 , and it is disputable, whether orthorhombic CePdAl 3 falls into the diagram at all or its commensurate type of order fits into the diagram with k z = 0.…”

“…9C. The amplitudes are refined to the values of m o ⊥ = 0.48 (11) µ B and m o = 1.18 (12) µ B , which also gives rise to an amplitude modulation, but only with two values: 0.48µ B for moments pointing along c-axis and 1.05µ B for the ones pointing 13 deg. away from the a-axis direction, see Fig.…”

“…Neutron diffraction studies in the magnetically ordered state in CeT Al 3 are so far reported for T = Cu and Au only. CeCuAl 3 exhibits an amplitude modulated, collinear, antiferromagnetic (AFM) structure, with k = (0.4 0.6 0) below T N = 2.7 K [12], while CeAuAl 3 exhibits a helical AFM structure with k = (0 0 0.52) below T N = 1.2 K [13]. Bulk properties measurements, such as heat capacity, electric resistivity, magnetization and magnetic susceptibility show that CeAgAl 3 is a ferromagnet at T C < 3.8 K [14].…”