Comparison of the nature of magnetism in α-Ni(OH)2 and β-Ni(OH)2

Abstract

For the two stable phases of Ni(OH)2, viz. α-Ni(OH)2 and β-Ni(OH)2, structural and magnetic properties are compared employing x-ray diffraction (XRD), scanning electron microscopy/transmission electron microscopy (TEM/SEM), and variation of the magnetization (M) with temperatures (2–350 K) and magnetic fields (up to ≈65 kOe). Both phases crystallize in the layered hexagonal structure with a=3.04 Å (3.12 Å) and c=23.6 Å (4.67 Å) for the α(β) phase with clear evidence for turbostraticity in the α-phase. From TEM/SEM, the β-phase consists of nanoplates of dimensions 30(10)×3(1) nm, whereas the α-phase has flowerlike morphology with petal thickness ≈5(1) nm. The low-field M versus T data for the zero-field-cooled/field cooled cases bifurcates at Tp=25 K (13 K) for the β(α) phase. For T>Tp, Curie–Weiss variation of M versus T is observed yielding positive θ=20.6 K (32 K) with μ=2.95 μB (3.13 μB) for the Ni2+ ions in the β(α) phase. The M versus H data at 2 K shows antiferromagnetic (ferromagnetic) like variation for the β(α) phase with dM/dH showing peaks at Hc1=28 kOe and Hc2=55 kOe for the β-phase. It is concluded that β-Ni(OH)2 is a metamagnet for T<TN=25 K, whereas α-Ni(OH)2 is a hard ferromagnet with Tc=13 K and domain structure for H<5 kOe.

Amorphous nickel hydroxide nanospheres by a green electrochemistry technique: structure, morphology and magnetism

“…But does not show an approach to the saturation state (50 emu g 21 at 5000 Oe), which can be attributed an asperomagnetism and/or spin-glass behavior of the amorphous Ni(OH) 2 sample. 3 Based on the experimental measurements and current studies, [23][24][25][26] we can conclude that in our study we have, for the first time, synthesized amorphous nickel hydroxide nanospheres with ferromagnetism below the Curie temperature of 16.5 K accompanied by high magnetization of 50 emu g 21 and high coercivity of 630 Oe at 5 K.…”

“…Note that the T C of the amorphous nickel hydroxide nanospheres is lower than that of the crystalline nickel hydroxide. [23][24][25][26] Fig. 4 shows the isothermal magnetization versus the applied field recorded at 5 and 15 K, respectively.…”

Nature of magnetic interactions in β-Co(OH)2 nanoparticles

“…Molecules of transition metal hydroxides always have surface‐absorbed water . Amount of this water can be easily determined with the help of a thermogravimetric analyzer, in which mass of sample is measured while being heated in air at a constant rate.…”

“…Transition metal hydroxides are known to exhibit unusual and interesting magnetic behavior . These materials also have many technological applications .…”

Nickel hydroxides and related materials: a review of their structures, synthesis and properties

“…We know of only the study by Rall et al [217,218] on α-Ni(OH) 2 · 3.3H 2 O in the form of flowers with a petal thickness of approximately 5 nm and with lattice constants of a = 3.0 Å and c = 8.6 Å. Comparative studies of the magnetic susceptibility of powdered samples of α-Ni(OH) 2 and β-Ni(OH) 2 yielded maxima at 13-16 K and 25 K, respectively, and a 40 times greater value for the field-cooled susceptibility in α-Ni(OH) 2 versus that in β-Ni(OH) 2 , indicating differences in their magnetic ordering.…”