The Phase Diagram and Exotic Magnetostrictive Behaviors in Spinel Oxide Co(Fe1−xAlx)2O4 System

Abstract

We report the magnetic and magnetostrictive behaviors of the pseudobinary ferrimagnetic spinel oxide system (1−x)CoFe2O4–xCoAl2O4 [Co(Fe1−xAlx)2O4], with one end-member being the ferrimagnetic CoFe2O4 and the other end-member being CoAl2O4 that is paramagnetic above 9.8 K. The temperature spectra of magnetization and magnetic susceptibility were employed to detect the magnetic transition temperatures and to determine the phase diagram of this system. Composition dependent and temperature dependent magnetostrictive behaviors reveal an exotic phase boundary that separates two ferrimagnetic states: At room temperature and under small magnetic fields (∼500 Oe), Fe-rich compositions exhibit negative magnetostriction while the Al-rich compositions exhibit positive magnetostriction though the values are small (<10 ppm). Moreover, the compositions around this phase boundary at room temperature (x = 0.35, 0.4, 0.45, 0.5) exhibit near-zero magnetostriction and enhanced magnetic susceptibility, which may be promising in the applications for magnetic cores, current sensors, or magnetic shielding materials.

Negative magnetostrictive paper formed by dispersing CoFe2O4 particles in cellulose nanofibrils

“…The maximum negative value of the CoFe 2 O 4 plate was − 90 ppm under a magnetic field of 217 kA/m. Bozorth et al 50 said that CoFe 2 O 4 has two magnetostriction coefficients and : and at 300 K. Since the easy magnetization axis of CoFe 2 O 4 is [100], correspondingly, it has a large negative and a small positive 51 , 52 . It is believed that the same phenomenon occurred.…”

Zinc and cobalt nano ferrites and their potential applications in environmental sustainability

“…More chemical stability, extraordinary mechanical hardness, and good coercivity [21] . The properties of CoFe2O4 and ZnFe2O4 can be enhanced by adding metal ions with different valency, coordinating to requirements [22] . The substitution of rare-earth ions in cobalt and Zinc ferrites made the study more interesting [23] .…”