Al doping effect on magnetic phase transitions of magnetoelectric hexaferrite Ba0.7Sr1.3Zn2

Abstract

We investigated the effect of Al doping in magnetic properties of the Y-type hexaferrite Ba 0.7 Sr 1.3 Zn 2 (Fe 1−x Al x) 12 O 22 (0 x 0.12), which exhibit field-induced magnetoelectric polarization. We find that Al doping increases the pitch of a spin helix and enhances c-axis magnetization, stabilizing longitudinal conical phases. These conical phases eventually collapse at x 0.10. These results suggest that competitions between easy-axis and easy-plane anisotropy fields play a key role in generating stable magnetoelectric polarization in Y-type hexaferrites.

Field‐Dependent Magnetoelectric Effects in Polycrystalline Co2Y‐Type Ba0.5Sr1.5Co2(Fe1−xAlx)12O22 Hexaferrites

“…As we known, two coexisting magnetic anisotropy fields, easy axis, and easy plane with respect to the c axis of the hexagonal lattice, are responsible for the heliconical order in Y-type hexaferrites. 18 For Co 2 Y hexaferrites, Co 2+ ions can contribute to additional anisotropy terms, 19,21 which makes the spin more difficult to rotate during magnetization reversal. Therefore, at low temperatures, most of the transverse conical can be maintained at zero field, leading to an irreversible M-H curve.…”

“…11,16 Chun et al 17 reported that the nonmagnetic Al 3+ ion replacement of the magnetic Fe 3+ ion can induce a giant ME susceptibility of 2.0 9 10 4 ps/m in Ba 0.5 Sr 1.5 Zn 2 (Fe 1Àx Al x ) 12 O 22 (Zn 2 Y) at x = 0.08 and 30 K. The improvement of its magnetoelectric properties was interpreted by the fact that Al-substitution can stabilize the longitudinal conical phase, which can turn into transverse conical structure by applying a low magnetic field. 18 In this work, we investigate the field-induced ME effect of Al-substituted Co 2 Y type Ba 0.5 Sr 1.5 Co 2 (Fe 1Àx Al x ) 12 O 22 hexaferrites. Co 2+ ions, different from Zn 2+ ions, are magnetic and they can contribute to the enhancement of the magnetic ordering temperatures.…”

57Fe NMR study of the magnetoelectric hexaferrite Ba0.5Sr1.5ZnKwon1, Yoon2, Lee3 et al. 2013Phys. Rev. B7040View full textAdd to dashboardCite

“…Indeed, it is proposed that Al doping suppresses magnetic anisotropy, and the reduction of magnetic anisotropy is plausibly the origin of the conical magnetic structures in BSZFAO. 13,16 Figure 4 shows the temperature dependence of the peak 1 frequency for BSZFO and BSZFAO in a zero magnetic field. The Bloch T 3/2 law fits well for both BSZFO and BSZFAO, meaning that the low-temperature excitation is gapless spin wave in ferromagnetic phase.…”

Broadband transverse susceptibility in multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22

“…The different magnetic structures change from planar helix to collinear ferrimagnetic ordering, with several intermediate commensurate magnetic spin phases with mixed conical structure, called I, II and III (the spin orientations in this phases can be seen in [4,8,19]). For each composition, some of the above, as well as alternate longitudinal conical (ALC) and transverse conical (TC) can take place at different values of temperature and applied magnetic field leading to a complex magnetic phase diagram [4,8,35,36]. Unless the spin induced ferroelectric order is usually attributed to the TC spiral system, other authors have suggested that the intermediate II and III spin systems can also promote electric polarization [1,4,37].…”