Published in
Institute of Electrical and Electronics Engineers, IEEE Transactions on Magnetics, 10(47), p. 2893-2896, 2011
DOI: 10.1109/tmag.2011.2151180
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Magnetic Structures of ${\hbox {Pr}}_{0.8}{\hbox {Lu}}_{0.2}{\hbox {Mn}}_{2}{\hbox {Ge}}_{2}$ and ${\hbox {Pr}}_{0.6}{\hbox {Lu}}_{0.4}{\hbox {Mn}}_{2}{\hbox {Ge}}_{2}$
,
A. J. Studer,
S. J. Campbell,
S. J. Kennedy,
R. Zeng,
S. X. Dou,
G. H. Wu
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Abstract
The magnetic structures of Pr0.8Lu0.2Mn2Ge2 and Pr0.6Lu0.4Mn2Ge2 have been determined by neutron powder diffraction over the temperature range 10-450 K. On cooling from the paramagnetic region the Mn sublattice of Pr0.8Lu0.2Mn2Ge2 orders in a similar manner to PrMn2Ge2 with first ab-plane intralayer antiferromagnetism (AFI) below T-N(intra) similar to 397 K followed by canted ferromagnetism (Fmc) at T-C(inter) similar to 330 K and then a conical (Fmi) spin structure below T-c/c similar to 192 K. The transition at T-C(Pr) = 35 K with related enhancement in magnetization, is assigned to the additional ferromagnetic contribution of the Pr sublattice leading to the combined (Fmc+F(Pr)). For Pr0.6Lu0.4Mn2Ge2 the transition from PM to AFI occurs at T-N(intra) similar to 375 K while the canted ferromagnetic (Fmc) state forms at T-C(intra) similar to 321 K. The increased Lu concentration of Pr0.6Lu0.4Mn2Ge2 destroys the incommensurate Fmi conical spin structure of Pr0.8Lu0.4Mn2Ge2. Rather, in common with similar mixed RT2X2 systems (e.g., La1-xYxMn2Si2, La1-xPrxMn2Si2), the Pr0.6Lu0.4Mn2Ge2 compound exhibits co-existence of the AFmc and Fmc phases on cooling from the pure Fmc state. Transformation to the combined ferromagnetic state (Fmc+F(Pr)) takes place on c-axis ordering of the Pr sublattice at T-C(Pr) similar to 31 K. In the region of phase co-existence, the Fmc unit cell is larger than the AFmc unit cell indicating strong magneto-structural coupling with a change of the lattice inducing a change of the magnetic state.