Hysteretic resonance frequencies and magnetization reversal in exchange biased polycrystalline F/AF bilayers

Spenato, D.; Pogossian, S. P.

doi:10.1016/j.jmmm.2004.07.018

Cited by 16 publications

(9 citation statements)

References 36 publications

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“…Conversely, the lower frequency branch at positive fields and the higher frequency branch at negative fields can be accessed when decreasing the value of the applied magnetic field. Although the hysteretic behavior of the f vs. H dependency is a rather rare phenomenon, it has been observed in a variety of materials including, e.g., exchangebiased bilayers 34 , BaFe 12 O 9 films 35,36 , thick Py films 25,37 , artificial spin ice 38 , and patterned nanostructures based on Py 39,40 . This effect allows the resonance frequency to be tuned as a function of the magnetic history, leading to a reconfigurable functionality in a Py film exhibiting stripe domains at a thickness of just 10 nm.…”

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confidence: 99%

Tunable ferromagnetic resonance in coupled trilayers with crossed in-plane and perpendicular magnetic anisotropies

Markó

Valdés-Bango

Quirós

et al. 2019

Applied Physics Letters

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A novel approach to tune the ferromagnetic resonance frequency of a soft magnetic Ni 80 Fe 20 (Permalloy = Py) film with in-plane magnetic anisotropy (IMA) based on the controlled coupling to a hard magnetic NdCo x film with perpendicular magnetic anisotropy (PMA) through a non-magnetic Al spacer is studied. Using transverse magneto-optical Kerr effect (TMOKE), alternating gradient magnetometry (AGM) as well as vector network analyzer ferromagnetic resonance (VNA-FMR) spectroscopy, the influence of both Co concentration and Al spacer thickness on the static and dynamic magnetic properties of the coupled IMA/PMA system is investigated. Compared to a single Py film, two striking effects of the coupling between IMA and PMA layers can be observed in their FMR spectra. First, there is a significant increase in the zero-field resonance frequency from 1.3 GHz up to 6.6 GHz, and second, an additional frequency hysteresis occurs at low magnetic fields applied along the hard axis. The maximum frequency difference between the frequency branches for increasing and decreasing magnetic field is as high as 1 GHz, corresponding to a tunability of about 20% at external fields of typically less than ±70 mT. The origin of the observed features in the FMR spectra is discussed by means of magnetization reversal curves.The magnetic properties of thin films and multilayers exhibiting stripe domains have been investigated extensively in both experiment and theory since their discovery more than half a century ago 1 . In recent years, research results on stripe domains have triggered the prospect of employing their unique properties in future microwave, magnonic, and spintronic devices with novel functionalities. The formation of stripe domains is the result of energy minimization as well as the competition between PMA (K ⊥ ) and shape anisotropy ( 1 2 µ 0 M 2 S ), which favor out-of-plane and in-plane magnetization, respectively. The ratio Q = 2K ⊥ /µ 0 M 2 S , known as reduced anisotropy or quality factor 2 , is commonly used to describe the extent of stripe domains. For moderate (Q < 1) to weak (Q 1) PMA, the magnetization tends to lie in the plane, but above a critical film thickness d cr , a ground state with stripe domains emerges. The latter is characterized by a perpendicular magnetization component alternating between up and down within a period λ . The critical thickness d cr is typically in the range of 20 -40 nm for moderate Q value materials such as amorphous NdCo alloys 3,4 , whereas for materials like Py with small values of Q, generally larger values of d cr = 170 -300 nm are found 5-8 . Intimately linked to the presence of stripe domains is the occurrence of a pseudo-uniaxial or rotatable anisotropy 9,10 , which is the result of the in-plane magnetization being aligned along the stripe direction. The latter, however, is not fixed as it can be reoriented by applya) Electronic

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confidence: 99%

Tunable ferromagnetic resonance in coupled trilayers with crossed in-plane and perpendicular magnetic anisotropies

Markó

Valdés-Bango

Quirós

et al. 2019

Applied Physics Letters

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“…The presence of "small pedestals" and field-separated sections of the dependence M͑H͒ indicates the possible existence of unusual, additional, stationary states which differ from the completely magnetically reversed states. Different theories [23][24][25] developed to explain the asymmetry of the hysteresis loop deploy additional assumptions, such as the presence of a nonzero angle between the direction of the FM magnetization and the AFM anisotropy axis or the presence of higher-order terms in the exchange interaction through the FM/AFM boundary. 23,24 On the other hand, it is shown in Refs.…”

Section: Introductionmentioning

confidence: 99%

“…Different theories [23][24][25] developed to explain the asymmetry of the hysteresis loop deploy additional assumptions, such as the presence of a nonzero angle between the direction of the FM magnetization and the AFM anisotropy axis or the presence of higher-order terms in the exchange interaction through the FM/AFM boundary. 23,24 On the other hand, it is shown in Refs. 10-13 that for sufficiently thick FM layers a portion of the anisotropy in M͑H͒ arises naturally in the simplest models of the EB phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Magnetization field-dependences and the “exchange bias” in ferro/antiferromagnetic systems. I. Model of a bilayer ferromagnetic

Grechnev

Kovalev

Pankratova

2009

Low Temperature Physics

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“…The interaction at the interface of layer ͑A͒ with ͑AF͒ gives rise to a unidirectional anisotropy called exchange anisotropy. [4][5][6][7][8][9][10][11][12][13][14][15][16] This anisotropy can be modeled as a magnetic field H E , the exchange anisotropy field. It is also found that in some cases, the unidirectional anisotropy axis and the anisotropy axis of the ferromagnetic layer ͑A͒ are not parallel but make an angle ␤ known as the offalignment angle.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of the torque curves in some magnetic multilayer systems

Layadi

2009

Phys. Rev. B

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Analytical expressions involving features from torque curves are derived for an exchange coupled ͓͑AF͒/͑F͔͒ bilayer, a coupled trilayer ͓͑F͒/͑N-M͒/͑F͔͒, and a magnetic tunnel junction ͑MTJ͒-like ͓͑AF͒/͑F͒/͑N-M͒/͑F͔͒ system. Included in the model are the exchange anisotropy field H E , the off-alignment angle ␤, the bilinear J 1 , and the biquadratic J 2 coupling strengths and the in-plane magnetocrystalline anisotropy fields of the two layers whose easy axes make an angle ␦. It will be shown how these parameters can be analytically derived from the torque curve. For the strong coupling case the MTJ-like system behaves as ͑AF͒/͑F͒ bilayer; for arbitrary ␦ value, the magnetic anisotropy field of the resulting system has a nonlinear relationship with the individual layer anisotropy fields.

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Hysteretic resonance frequencies and magnetization reversal in exchange biased polycrystalline F/AF bilayers

Cited by 16 publications

References 36 publications

Tunable ferromagnetic resonance in coupled trilayers with crossed in-plane and perpendicular magnetic anisotropies

Tunable ferromagnetic resonance in coupled trilayers with crossed in-plane and perpendicular magnetic anisotropies

Magnetization field-dependences and the “exchange bias” in ferro/antiferromagnetic systems. I. Model of a bilayer ferromagnetic

Theoretical study of the torque curves in some magnetic multilayer systems

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