Magnetic properties of Ni2+ clusters in NaY zeolite

Abstract

We have investigated the magnetic properties of Ni 2+ exchanged NaY zeolite by using a direct current magnetization technique. At T Ͼ 5 K, the M vs H / T curves superimpose and these curves could be fitted well using a Langevin function with a log-normal distribution of moments. The mean spin-cluster moment has been found to be ϳ3.3 B . The deviation from the superposition of the M vs H / T curves is observed at T Ͻ 5 K indicating the building up of a spin-spin correlation between Ni clusters below 5 K. The zero-field-cooled and field-cooled magnetization curves show branching at low temperatures ͑T Յ 5 K͒ under low applied magnetic fields ͑H Յ 1 kOe͒ with a peak in the zero-field-cooled magnetization curves. A log-normal distribution of spin-freezing/blocking temperature has been observed with mean spin-freezing/blocking temperature ϳ3.0 K. The peak temperature T g decreases with increasing field and follows the de Almeida-Thouless ͑AT͒ line ͓1 − T g ͑H͒ / T g ͑0͔͒ ϰ H 2/3 . The extrapolation of the AT line gives the spin-freezing temperature T g ͑0͒ Ϸ 3.29 K.

Magnetic clustering of Ni2+ ions in metal-ceramic nanocomposites obtained from Ni-exchanged zeolite precursors

“…The resulting effective number of Bohr magnetons per paramagnetic ion n eff is reported in Table I also. The quantity  eff = n eff  B turns out to be compatible with the magnetic moments on Ni 2+ ions dispersed in zeolites available in the literature [60][61][62][63][64] and indicates that the paramagnetic units in our nanocomposites are single bivalent Ni ions (at high temperatures at least). In nanocomposites resulting from zeolite A, the effective magnetic moment is lower and closer to the ideal value for isolated Ni ions with almost complete quenching of the orbital angular momentum.…”

Evidence for the Existence of Oxygen Clustering and Understanding of Structural Disorder in Prussian Blue Analogues Molecular Magnet M1.5[Cr(CN)6]·zH2O (M = Fe and Co): Reverse Monte Carlo Simulation and Neutron Diffraction Study

“…Hence, a deeper understanding of local structure/disorder at the atomic scale is highly desirable. Some examples of disordered materials are (i) materials showing small deviation from perfect crystallinity: In–Ga–As semiconductor alloys, , (ii) crystalline materials showing significant structural disorder: nanophase LiMoS 2 , (iii) completely disordered materials: Ca–Al–Si–O glasses, (iv) materials showing no positional but chemical disorder: metallic Cu 3 Au, (v) disorder in organic materials: ferrocene, (vi) colossal magnetoresistance (CMR) materials with local dynamic distortions, (vii) zeolites with host–guest systems, , and (viii) molecular disorder in C 60 and related compounds, etc. In addition, one class of the crystalline materials which possesses structural disorder (static in nature) are Prussian blue analogues (PBA), which have attracted great attention recently because of their novel magnetic functionalities as well as other properties, such as magnetic pole inversion, , photomagnetic behavior, zero/negative thermal expansion, etc.…”

Presence of Cluster Spin-Glass Phase in Naturally Grown Bilayered Brownmillerite Compound Ca[sub 2.4]La[sub 0.1]Sr[sub 0.5]GaMn[sub 2]O[sub 8]

“…The dc-magnetization measurements were carried out using a commercial (Oxford Instruments) Vibrating Sample Magnetometer (VSM) as a function of temperature and applied magnetic field over the temperature range of 5 T (K) 320 and field range of r10 kOe, respectively. This is in contrast with a monotonous increase of FC magnetization expected for a superparamagnet [6,7]. After applying a magnetic field at 5 K, the magnetization was measured in the warming cycle with the field being on.…”