Effect of Al on the structural and magnetic properties of Er₂Co_17−xAl_xcompounds

Abstract

Powder x-ray diffraction and magnetization measurements were employed to investigate the effect of Al on the structural and magnetic properties of Er 2 Co 17−x Al x compounds with 0 x 4. Al substitution leads to a monotonic increase in the lattice parameters and an approximately linear decrease in the saturation magnetization. The Curie temperature is also found to decrease with Al concentration. Large thermomagnetic irreversibility seen in these compounds has been attributed to the domain wall pinning effect. The temperature variation of magnetization shows compensation points in the compounds with x = 3 and 4. The field-cooled magnetizations of these two compounds in low fields are found to be negative at temperature below the compensation temperatures, which has been explained on the basis of the temperature variations of the exchange coupling strengths of Er and Co sublattices. The easy magnetization direction at room temperature is found to be along the c-axis in all the compounds. The first order anisotropy constant at room temperature is found to increase with Al concentration, which has been attributed to the increase in the axial anisotropy of both the Er and Co sublattices as a result of Al substitution.

Hard magnetic properties of ErCo7−xCux [0.3⩽x⩽1] system

“…However, since the observed values are found to be lower than the values expected from the simple dilution model, we feel that the chemical effect arising from the charge transfer between Cu and the 3d band of Co may also be contributing to the reduction in M s with x. A similar reduction in the M s has been observed in Al-substituted 1:12 and 2:17 compounds [4,16].…”

“…A large difference between the ZFC and FC magnetization, known as thermomagnetic irreversibility, is observed in all these compounds. We attribute this to the domain wall pinning effect [16,17]. Domain wall pinning effect also manifests in the M-H isotherms at low temperatures, as shown in Fig.…”

“…where a J is the Stevens factor, r 4f is the mean radius of the 4f electron cloud, J is the total angular momentum and A 0 2 is the second-order crystal field parameter [3,16]. Since a J is positive for Er 3+ ion and A 0 2 is negative for the 1:7 structure, the Er anisotropy is axial according to Eq.…”

Effect of Y substitution on the structural and magnetic properties of Dy1−xYxCo5 compounds

“…It can be seen that the M s value at 5K is less than that at 300 K in all the compounds except YCo 5 , which implies that the coupling between the R and TM sublattices is ferrimagnetic in compounds with 0≤x<1 while YCo 5 is a ferromagnet. From the M-H plots at 300 K, it can be inferred that the Curie temperatures of this series of compounds is above room 10,11 Furthermore the compounds except DyCo 5 and YCo 5 show anomalies (indicated by arrows) in the M vs. T plots. The temperature corresponding to the anomaly is found to show a systematic decrease as Y concentration increases from 0.2 to 0.8, as can be seen from Table 1.…”

Competing soft dielectric phases and detailed balance in thin film manganites

“…In mixed-valence manganites, the disorder [8] and strain [9] based explanations have recently been augmented by a model describing an "electronically soft"coexistence, where the phase separation is driven by delocalized thermodynamic physics [10]. This theory has broad implications for complex oxides with coexisting and competing phases [11][12][13], however, evidence for 'electronically soft' phases has yet to be provided.…”