Spectroscopic and Magnetic Properties of Co_1.7Mn_0.3(OH)PO₄

Abstract

Co 1.7 Mn 0.3 (OH)PO 4 has been prepared under mild hydrothermal conditions and characterized from powder X-ray diffraction. IR data are characteristic of three distinct features corresponding principally to the vibrations of the hydroxide and [PO 4 ] 3Ϫ anions. UV-Visible studies show the existence of bands ascribed to the chromophores of Co ions in two coordination polyhedra, octahedral and trigonal bipyramidal. The magnetic behaviour indicates the existence of antiferromagnetic interactions as predominant. Magnetization measurements show the presence of two maxima at 65 K and 9 K, respectively. The first peak was attributed to a three-dimensional antiferromagnetic ordering and the second one reveals the possible existence of a spin-glass like state. The substitution of Co 2ϩ (S ϭ 3/2) by Mn 2ϩ (S ϭ 5/2) ions at about 15 % keeps the two magnetic transitions observed in the non-sub-1847 stituted phase. ZFC-FC curves show magnetic irreversibility at temperatures just below T N due to the spin decompensations in Co 1.7 Mn 0.3 (OH)PO 4 . The remanent magnetization indicates higher ferromagnetic interactions at lower temperatures than that observed in the ordered Co 2 (OH)PO 4 phase. These results could be attributed to the existence of a spin-glass state similar to that exhibited by the Co 2 (OH)PO 4 and substituted Co 2Ϫx M x (OH)PO 4 (M ϭ Ni, Cu; x ϭ 0.1Ϫ0.3) compounds. A comparative magnetic study with the analogous Ni 2ϩ (S ϭ 1) and Cu 2ϩ (S ϭ 1/2) phases is carried out.

Synthesis, Spectroscopic and Magnetic Properties of the Co2(OH)(PO4)1–x(AsO4)x [0 ≤ x ≤ 1] Solid Solution

“…In these compounds the TRM starts to increase below T N and then remains almost constant down to 4.2 K. This behavior shows that the intensity of the ferromagnetic component is virtually independent of the temperature. The Co 2 (OH)-(PO 4 [ [16][17][18]26] Therefore, the weak ferromagnetic coupling shown in Co 2 (OH)PO 4 [16] remains until there is a 75 % substitution of arsenate, developing into a magnetization in different stages for higher arsenate concentration, as was observed in the Co 2 (OH)AsO 4 phase. [19] In summary, the magnetic behavior of the Co 2 (OH)-(PO 4 ) 1-x (AsO 4 ) x [0 Յ x Յ 1] phases shows a magnetic evolution from a three-dimensional antiferromagnetic system with a spin glass state, Co 2 (OH)PO 4 , to an incommensurate antiferromagnetic ordering at lower temperature, in Co 2 (OH)AsO 4 phase.…”

Co11Li[(OH)5O][(PO3OH)(PO4)5], a Lithium-Stabilized, Mixed-Valent Cobalt(II,III) Hydroxide Phosphate Framework

“…The compound was found to be the first ordered cobalt phosphate that exhibits a three-dimensional antiferromagnetic long-range order below T = 70 K and a spin-glass-like state with a blocking temperature of 13 K. This spin-glass-like behavior was related to a magnetic frustration of the Co 2+ ions in the [CoO 5 ] dimers due to the existence of antiferromagnetic interactions between the neighboring [CoO 6 ] ∞ chains as well as a ferromagnetic interaction between the chains and the dimers . In a number of studies by de Pedro and co-workers, − it was further demonstrated that the magnetic properties of adamite-type Pnnm -Co 2 (OH)­PO 4 can be modified by substituting Co by other magnetic transition-metal ions such as Ni, Cu, and Mn. Furthermore, also the properties of solid solutions of phosphate and arsenate, Co 2 (OH)­(PO 4 ) 1– x ­(AsO 4 ) x ( x = 0–1), have been explored…”

Sinusoidal magnetic structure in a three-dimensional antiferromagneticCo2(OH)AsO4: Incommensurate-commensurate magnetic phase transition

“…11 The partial substitution of transition-metal ions in the structure severely affects the magnetic properties 14,15 giving rise to the evolution of the 3D antiferromagnetic system in the Co 2−x Cu x ͑OH͒PO 4 solid solution 15 up to a spin-gap system in the Cu 2 ͑OH͒PO 4 phase, 16 the spin-glasslike state in the ͑Co, Ni͒ 2 ͑OH͒PO 4 detected below 10 K, 14 or the higher ferromagnetic interactions at lower temperatures in Co 1.7 Mn 0.3 ͑OH͒PO 4 coexisting with a similar spin-glass state observed in the nonsubstituted cobalt hydroxy phosphate. 17 The similar ability of AsO 4 3− and PO 4 3− tetrahedra to stabilize anionic frameworks and the greater size of the AsO 4 3− anions predict some differences in the crystal packing features that could modify the complex magnetic properties exhibited in these phases. In this work, we present a deeper magnetic study of Co 2 ͑OH͒AsO 4 in order to determine ͑i͒ the nature of the main magnetic interactions and their anomalies, ͑ii͒ the magnetic structure of the low-temperature ordered phase, and ͑iii͒ the magnetic variations with respect to the isostructural Co 2 ͑OH͒PO 4 compound.…”