Structural and magnetic phase transitions of kagome-like compounds REBaCo4O7 (RE=Dy, Ho, Er, Tm, Yb, Lu)

Dramatic effect of A-site substitution upon the structure and magnetism of the “114” CaBaCo4O7cobaltite

“…Starting from the valence distribution of undoped phase CaBa[Co 3+ ] T [Co 2+ 2 Co 3+ 1 ] K O 7 and bearing in mind that the symmetry remains orthorhombic after doping with Co 2+ , we can propose that in a first step the additional Co 2+ can be distributed equally between the two Co 3+ sites of T and K layers, respectively, according to the formula Ca 0. 9 Other extreme hypotheses would be that the additional 0.1 Co 2+ would sit either only in the T layer or only in the K layer. Nevertheless, any of these three scenarios does not involve a high disordering of the Co 2+ and Co 3+ species and consequently cannot explain alone the formation of the glassy state at the expense of ferrimagnetism.…”

“…Thus, as for the hole-doped system, we believe that this small excess of Co 2+ induces a much larger partial cationic disordering in both the T and K layers, according to the formula Ca 0. 9 different sites, characterized by the degree of disorder λ (λ being significantly smaller than 0.5), which is responsible for the disordered distribution of the Co 2+ /Co 3+ AFM and Co 2+ /Co 2+ , Co 3+ /Co 3+ FM interactions, leading to magnetic frustration.…”

“…[4][5][6][7][8][9][10][11] One important feature of these compounds deals with the fact that the transition element, in its mixed valent state Co 2+ /Co 3+ , accommodates a pure tetrahedral coordination. This is quite unique with respect to other strongly correlated oxides, where the framework is octahedral, and it should have a great impact upon the magnetic properties of these cobaltites, leading to cobalt and oxygen to triangular (T) sublattices favorable to a geometric frustration.…”

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

“…The large family of the ''114'' cobaltites LnBaCo 4 O 7 (Ln ¼ lanthanide or Y) with various substitutions at the Ln as well as the Co sites has been the subject of numerous investigations [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] due to its attractive magnetic properties showing geometric frustration in competition with magnetic ordering, and associated with a structural transition from the hexagonal to orthorhombic symmetry. Besides these, another ''114'' cobaltite, CaBaCo 4 O 7 , which is characterized by a large orthorhombic distortion at all temperatures from 4 K to 400 K, is unique in that it is the only member of this family which exhibits a ferrimagnetic ground state at a low temperature (T C ¼ 60 K).…”

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.…”