Magnetism of the “114” orthorhombic charge ordered CaBaCo4O7 doped with Zn or Ga: a spectacular valency effect

Abstract

The substitution of zinc and gallium for cobalt in CaBaCo 4 O 7 has allowed the oxide series CaBaCo 4Àx M x O 7 (M ¼ Zn, Ga) with 0.02 # x # 1.20, belonging to the ''114'' structural family, to be synthesized. From the structural view point two domains can be distinguished: for x # 0.70 (for Zn) and x # 0.90 (for Ga), the orthorhombic symmetry of CaBaCo 4 O 7 is retained (albeit with reduced orthorhombic distortion for higher values of x), whereas for x $ 1.0 the symmetry is hexagonal. More importantly, we observe a contrasting effect of the valency of Zn 2+ and Ga 3+ upon the magnetic properties of the doped CaBaCo 4Àx M x O 7 cobaltites in the low doping regime (x # 0.40). While the doping of Ga 3+ for Co 3+ leads to a progressive disappearance of ferrimagnetism with a simultaneous appearance of magnetic frustration, the doping of Zn 2+ for Co 2+ induces an abrupt switching from ferrimagnetism to antiferromagnetism. We explain these effects as arising from a perturbation of the ferromagnetic Co 2+ chains which form the magnetic structure of CaBaCo 4 O 7 in the case of substitution by zinc, and a destruction of the magnetic order by substitution of Ga 3+ on the Co 3+ sites in the case of gallium doping. For higher substitution levels (x $ 0.50), both Zn and Ga substitutions lead to a spin glass behavior, irrespective of the symmetry, orthorhombic or hexagonal.

Substitution site and effects on magnetism in Sr-for-Ca substituted CaBaCo4O7

“…Other cationic substitutions at the Co and Ba sites have shown to affect the magnetic properties [13][14][15] . This paper focuses in the room-temperature structural aspects of the Sr-substitution, given the importance of correctly identifying the substitution sites in the structure 16 .…”

Structure evolution in “114” oxides CaBaZn2Ga2−xAlxO7 (x = 0, 1, 2) and layered cationic ordering in tetrahedral sites for CaBaZn2Al2O7

“…By introducing larger cations (Zn 2+ and Ga 3+ ) into the tetrahedral sites, the symmetry for those doped compounds, namely, CaBaCo 4−x Zn x O 7 (x ≥ 0.8) and CaBaCo 4−x Ga x O 7 (x ≥ 1.0), changes to P6 3 mc. 30 This is reasonable so far. The interesting phenomenon is that the compounds CaBaCo 4−x Al x O 7 (x ≥ 0.4) with smaller average Tsizes compared to CaBaCo 4 O 7 also crystallize in the hexagonal symmetry.…”

The YBaCo4O7+δ‐Based Functional Oxide Material Family: A Review

“…Although barium is under-bonded in YBaCo 4 O 7 , yttrium is over-bonded and accordingly can be readily substituted by other smaller or equal-sized trivalent rare-earth elements from Dy to Lu [5,7,28,34,40,43,46,47,50,56,57,[59][60][61][62][63][64][65] and also by divalent Ca [26,29,30,48,56,58,[66][67][68][69][70][71][72][73][74][75][76][77][78][79] and trivalent In. [56] Furthermore, solubility of up to 5 % has been reported for trivalent Bi.…”

“…[56] In addition to iron, many other metal species have been investigated as possible substituents for cobalt: Mn, Ni, Cu, Zn, Al, Ga, and Li. [77,87] Zn, [25,[28][29][30]56,57,66,69,72,73,77,[88][89][90][91][92][93][94] Ga, [35,57,72,86,87,92,95] and Al [30,37,44,56,64,67,69,70,90,96,97] substitutions have been studied extensively owing to the stability they bring to the parent phase. [77,87] Zn, [25,[28][29][30]56,57,66,69,72,…”

“…[108,116] The reason for these somewhat different magnetic properties is the higher average Co valence in CaBaCo 4 O 7+δ compared with the RBaCo 4 O 7+δ phases and the released geometric frustration resulting from the buckling of the Kagome layers. [73,87] On the other hand, trivalent Gafor-Co [72] or Al-for-Co substitutions give rise to magnetic frustration. [117] When CaBaCo 4 O 7+δ is doped with aliovalent cations, monovalent Li or divalent Zn, the ferromagnetic behavior changes to antiferromagnetism.…”