Current-induced nonlinear magnetoelectric effects in strontium hexaferrite

Abstract

We report on the first observation of nonlinear magnetoelectric effects at room temperature due to a DC current in the ferrimagnetic M-type strontium hexaferrite platelets. Utilizing microwave measurement techniques and data on the shift in magnetic mode frequencies, it was found that a DC current along the hexagonal c-axis resulted in a significant decrease in the saturation magnetization and an increase in the uniaxial magnetocrystalline anisotropy field. These changes in the magnetic order parameters were directly proportional to the square of applied electric field and were found to be much higher than variations due to Joule heating. A phenomenological theory that takes into account the current-induced magnetobielectric effects (MBE) is proposed. Expressions for coupling coefficients for MBE have been obtained and have been calculated from the variations in magnetic order parameters. The electric field E (or current) tuning of the magnetic modes in SrM reported here is orders of magnitude stronger than strain mediated E-tuning of magnetic resonance in hexaferrite-ferroelectric composites. The non-linear ME effects in the hexaferrite, therefore, open up an avenue for the realization of E-tunable broad-band microwave and millimeter wave ferrite signal processing devices such as resonators and filters.

Direct imaging of dopant sites in rare-earth element-doped permanent magnet and correlated magnetism origin

“…[1][2][3][4][5][6] Besides, the recent observation of a large room-temperature multiferroic effect in hexaferrite makes them even more attractive in scientific research and novel applications. 7 Thus, there have been many attempts to reduce their cost and further improve their magnetic performances. Among them, slight doping of rare-earth elements has proven to be an effective way.…”

Current tunable barium hexaferrite millimeter wave resonator

“…Figure shows vs. p and a linear variation evident from the data. According to the model for current induced non‐linear ME effects in M‐type ferrites variations in M 0 and are predicted to be linearly with electric power . Thus, it is clear from Equations and that also has to be a linear function of p .…”

“…These substituted hexaferrites have a complex conical magnetic structure and thus their linear ME‐effects are allowed by crystallographic and magnetic symmetry . We reported recently on the observation of current induced non‐linear ME effects in single crystal SrM that leads to variations in the magnetization and anisotropy field and alters the magnetic mode frequencies . In this work the ME effect is utilized to tune the frequency of a BaM resonator.…”

Анизотропия Гигантских Нелинейных Магнитоэлектрических Эффектов В Гексаферритах Со Структурой Магнитоплюмбита

“…Используя их, находим, что намагниченность M z и константа анизотро-пии K u линейно зависят от плотности подводимой элек-трической мощности с коэффициентами пропорциональ-ности −(11.5 ± 1.2) G · mm 3 /W и −(1160 ± 120) erg/W. В то же время для случая тока, протекающего вдоль гексагональной оси кристалла [11], соответствующие величины равны примерно −2 G · mm 3 /W и −170 erg/W, т. е. в 6−7 раз меньше. Заметим, что это соотноше-ние ( " анизотропия МЭ эффекта") оказывается одного порядка с анизотропией электрической проводимости в гексаферритах M-типа [17].…”

“…Приме-нение гексаферритов в составе композитных материалов показало принципиальную возможность электрического управления резонансной частотой таких структур в мил-лиметровом диапазоне [9,10], но полученные величины перестройки оказались слишком малыми для практи-ческого применения. Недавно в гексаферрите стронция были экспериментально обнаружены нелинейные МЭ токовые эффекты, которые по величине на порядок больше наблюдаемых в гетероструктурах [11]. Их можно назвать гигантскими по аналогии с гигантским магнито-сопротивлением.…”