Anisotropic characteristics and improved magnetic performance of Ca–La–Co-substituted strontium hexaferrite nanomagnets

Abstract

Recent studies on next-generation permanent magnets have focused on filling in the gap between rare-earth magnets and rare-earth-free magnets, taking into account both the cost-effectiveness and magnetic performance of the magnetic materials. As an improved rare-earth-free magnet candidate, here, Ca-substituted M-type Sr-lean hexaferrite particles within a nano- to micro-scale regime, produced using an ultrasonic spray pyrolysis method, are investigated. Theoretically, the maximum coercivity (Hc) can be achieved in submicron Sr-ferrite crystals (i.e., 0.89 μm). The plate-like resultants showed a significant enhancement in Hc, up to a record high of 7880.4 Oe, with no deterioration in magnetization (M: 71–72 emu/g). This resulted in more favorable magnetic properties than those of the traditional Sr–La–Co ferrites. On the basis of microstructural analysis and fitting results based on the law of approach to saturation method, the Ca-substitution effects on the change in size and anisotropic characteristics of the ferrite particles, including pronounced lateral crystal growth and a strong increase in magnetocrystalline anisotropy, are clearly demonstrated. The cost-effective, submicron, and Ca-substituted Sr-ferrite is an excellent potential magnet and moreover may overcome the limitations of traditional hard magnetic materials.

Towards hard-magnetic behavior of CoFe2O4 nanoparticles: a detailed study of crystalline and electronic structures, and magnetic properties

“…9. Determination of M s can be based on the law of approach to saturation (LAS), in which H -dependent M obeys the following expression: 50 where a ′ and χH associated with the inhomogeneities and spontaneous magnetization of domains, respectively, are ignorable as considering a homogeneous ferromagnet at low temperatures and high fields. In other words, eqn (1) can be rewritten as:where b is a parameter associated with the magneto-crystalline anisotropy.…”

Recent Progress in Hexagonal Ferrites Based Composites for Microwave Absorption

“…[ 215 ] Efforts have been made to enhance the magnetic characteristics of hexaferrite by cationic substitution to meet a variety of applications. [ 148,216 ] These includes efforts on altering the intrinsic properties of hexaferrites by replacing with either single or multiple trivalent metal ions such as La 3+ , [ 217–221 ] Tb 3+ , [ 222,223 ] Nd 3+ , [ 138–140,224–226 ] Eu 3+ , [ 227 ] Dy 3+ , [ 228,229 ] Sm 3+ , [ 230,231 ] Cr 3+ , [ 232,233 ] Al 3+ , [ 185,186,234,235 ] Gd 3+ , [ 236–238 ] Sc 3+ , [ 239 ] Er 3+ , [ 240–242 ] Pr 3+ , [ 243 ] Yb 3+ , [ 244 ] Ce 3+ , [ 245 ] La 3+ –Pr 3+ , [ 246 ] La 3+ –Nd 3+ , [ 247 ] Nd 3+ –Sm 3+ , [ 248 ] Nb 3+ –Y 3+ , [ 249 ] La 3+ –Ce 3+ , [ 250 ] Er 3+ –Cr 3+ , [ 251 ] Dy 3+ –Nd 3+ –Pr 3+[ 252 ] or a suitable mix of divalent and trivalent ions such as Tb 3+ –Mn 2+ , [ 253 ] Nd 3+ –Co 2+ , [ 254 ] Gd 3+ –Co 2+ , [ 255 ] Pr 3+ –Mn 2+ , [ 256 ] Sm 3+ –Co 2+ , [ 257 ] La 3+ –Co 2+ , [ 258 ] La 3+ –Mn 2+ , [ 259 ] Pr 3+ –Co 2+ , [ 260 ] Cu 2+ –Cr 3+ , [ 261 ] Al 3+ –Mg 2+ , [ 262 ] Ce 3+ –Zn 2+ , [ 263 ] Ce 3+ –Co 2+ , [ 264 ] Gd 3+ –Mn 2+ ‐Co 2+ , [ 265 ] Ca 2+ –La 3+ –Co 2+[ 266 ] or tetravalent Zr 4+[ 267 ] or a divalent and tetravalent ions such as Co 2+ –Si 4+ , [ 268 ] Cu 2+ –Zr 4+,[ 269 ] Zr 4+ –Co 2+ , [...…”

Effect of the neodymium doping on the magnetic and structural properties of the Sr-hexaferrite obtained by the Pechini method

“…It has even been reported that in some cases, there is a preferential stacking (arrangement) in hexagonal-shaped particles. Therefore, the crystals tend to grow perpendicular to the c-axis, which makes the easy stacking of the platelet-like particles [44]. This effect is most likely due to the magnetic interactions between platelets [45].…”