Magnetic Properties of theRE₂Pt₆X₁₅(RE= Y, La–Nd, Sm, Gd–Lu;X= Al, Ga) Series

Abstract

The members of the RE2Pt6Al15 (RE = Ce–Nd, Sm, Gd–Yb) and RE2Pt6Ga15 (RE = Y, La–Nd, Sm, Gd–Lu) series have been synthesized from the elements via arc‐melting followed by annealing in an induction furnace. Isotypism of Ho2Pt6Al15 with orthorhombic (3+1)D commensurately modulated Sc2Pt6Al15 [Cmcm(α,0,0)0s0, α = 2/3] was observed from single‐crystal diffraction data. The diffraction pattern shows the same satellite reflections pattern as the prototype, therefore the same modulated superstructure was refined. Full ordering of the Pt and Al atoms within the [Pt6Al15]δ– polyanion was observed. The lattice parameters of the averaged hexagonal structure were refined from powder X‐ray diffraction experiments and agree well with previous reports on these compounds. The X‐ray pure polycrystalline samples of both series were studied with respect to their magnetic properties. The susceptibility data of all investigated compounds show experimental magnetic moments close to the free ion values of the RE3+ cations and antiferro‐/ferrimagnetic ordering at low temperatures with Curie temperatures up to TC = 16.8(1) K for Gd2Pt6Ga15. Both, Sm2Pt6Al15 and Sm2Pt6Ga15 show the typical van Vleck type behavior along with antiferromagnetic ordering at a Néel temperature of TN = 4.5(1) K (Al) and ferrimagnetic ordering at TC = 6.5(1) K (Ga). Yb2Pt6Al15 exhibits ytterbium in the trivalent oxidation state, while for Yb2Pt6Ga15 a divalent state of the Yb atoms was observed.

Synthesis, Crystal Structure, Local Structure, and Magnetic Properties of Polycrystalline and Single-Crystalline Ce2Pt6Al15

“…Moreover, the existence of streak scattering along the [001]-direction indicates stacking disorder in the superstructure. Overall observations have led to the conclusion of the formation of R 2 X 3 honeycomb layers with local orthorhombic symmetry (space group 63 (Cmcm)) [25], as shown in Figure 1b,d. Most of the research focused on this system has utilized the X-ray diffraction method; however, X-ray diffraction is not sensitive enough for analysis of the stacking disorder in the crystal structure.…”

“…The R 2 T 6 X 15 (R = rare earth and actinide, T = Pt, Pd, Fe, Ni, X = Al, Ga, Si) system is one of the candidates for determining frustrated systems with honeycomb structure. Several rare-earth and uranium compound series belonging to this system, such as R-Pd-X [9], R-Pt-X [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], R-Ni-(Ga, Ge) [26], and R-Fe-Si [27][28][29], have been reported. In the early stages of research, this crystal structure was solved as the hexagonal Sc 0.6 Fe 2 Si 4.9 -type structure (space group 194 (P6 3 /mmc)) [19], as shown in Figure 1a,c.…”

“…There have been contradicting reports on the physical properties of Ce 2 Pt 6 Al 15 . The polycrystalline Ce 2 Pt 6 Al 15 prepared by arc melting (AM-Ce 2 Pt 6 Al 15 ) was an antiferromagnet with T N = 2.6 K [25], while Ce 2 Pt 6 Al 15 prepared by unknown method [30] and the single-crystalline [31] Ce 2 Pt 6 Al 15 prepared using flux method (F-Ce 2 Pt 6 Al 15 ) exhibited NFL behavior. As a possible origin of the sample dependence, the difference in the local crystal structure arising from different preparation methods was inferred.…”

Electronic and structural properties of Y6Pt13X4, site occupancy variants of the Ba6Na16N subnitride (X = Al, Ga)

“…1–17 Among the advances of the last decade, one should mention the extensive structural studies for the series (i) RE 10 TAl 3 , 18 RE 4 TAl 19,20 and Ho 6 Co 2 Ga-type compounds 21 and (ii) RE 4 T 9 Al 24 , 22 RE 2 T 6 Al 15 and RE 3 T 4 Al 12 , 23,24 RETAl 2 25 for the RE- rich and Al (or Ga)-rich compounds, respectively as well as the numerous investigations of their responses to electrical and magnetic stimuli. 26–30…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Among the advances of the last decade, one should mention the extensive structural studies for the series (i) RE 10 TAl 3 , 18 RE 4 TAl 19,20 and Ho 6 Co 2 Ga-type compounds 21 and (ii) RE 4 T 9 Al 24 , 22 RE 2 T 6 Al 15 and RE 3 T 4 Al 12 , 23,24 RETAl 2 25 for the RE-rich and Al (or Ga)rich compounds, respectively as well as the numerous investigations of their responses to electrical and magnetic stimuli. [26][27][28][29][30] Significantly less ternary RE aluminides and gallides are known for the transition metal-rich concentration range, particularly with platinum as a transition metal substitute (Pt ≥ 50 at%). Besides the well-known series of CaCu 5 -type ternary derivatives, [31][32][33] several new ternary RE platinum-rich compounds with Al have been reported more recently.…”