Low-energy magnetoelectric control of domain states in exchange-coupled heterostructures

Al‐Mahdawi, Muftah; Pati, Satya Prakash; Shiokawa, Y.; Ye, Shujun; Nozaki, Tomohiro; Sahashi, M.

doi:10.1103/physrevb.95.144423

Cited by 28 publications

(52 citation statements)

References 52 publications

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“…From the negative H ex , we can speculate that the surface spin of Al‐Cr 2 O 3 was in the negative direction of Y axis, same as the M para direction. This is actually consistent with our previous magnetoelectric constant measurement . The surface spin direction of Al‐Cr 2 O 3 was not changed from 10 to 100 K from the vertical shift of the hysteresis loops.…”

supporting

confidence: 51%

“…Other possibilities may still exist, including the interfacial defect and/or net magnetization of the AFM grain boundary. Nevertheless, the antiferromagnetic and magnetoelectric properties of Cr 2 O 3 remained after Al doping, which was confirmed in our recent work . The areal magnetization at 10 K linearly depended on the thickness of Al‐Cr 2 O 3 as shown in Figure S1a, Supporting Information suggesting that the M para by Al doping was related to the volume effect.…”

mentioning

confidence: 98%

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Spin Reversal Mechanism of a Perpendicular Exchange Bias System with an Antiferromagnet Incorporating a Parasitic Ferromagnetism

Shiokawa

Pati

et al. 2019

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Aluminum doping produced the parasitic magnetization (M para ) with high coercivity in 20 nm thin antiferromagnetic Cr 2 O 3 films. By using the large coercive force of M para , whose direction is the same as the antiferromagnetic Cr 2 O 3 surface spin, antiferromagnetic spin reversal can be detected through the vertical shift of the hysteresis loop of an antiferromagnetic-Cr 2 O 3 / ferromagnet perpendicular exchange bias (PEB) coupling system. By analyzing both antiferromagnetic and ferromagnetic spin reversals in response to external magnetic field and temperature, each spin reversal mechanism in a PEB system is clarified. It is found that the competition among Zeeman energy due to M para , exchange coupling energy, and antiferromagnetic anisotropy energy decides the antiferromagnetic spin direction and, accordingly, PEB sign under different cooling fields, different temperatures, and different swept magnetic fields for PEB systems. This work might contribute to a deep understanding of spin reversal mechanism in a perpendicular exchange bias system.Antiferromagnetic spin is difficult to detect and control, which enables its hardness for an external magnetic field. Moreover, an antiferromagnet (AFM) also has ultrafast spin dynamics to terahertz, which makes its switching much faster than that of a ferromagnet (FM). Therefore, AFMs are widely studied in many fields. [1][2][3][4] In particular, nonvolatile magnetic random-access memory (MRAM) is expected to replace volatile DRAM and SRAM in computing systems. [5] The exchange bias at the interface between AFM and FM is an important physical phenomenon, of which the hysteresis loop shift left (negative) or right (positive) of field axis could be obtained because of exchange bias coupling. [6] The in-plane exchange bias has already been used in hard-disk drive heads. Perpendicular exchange bias (PEB) devices attract more attention because of their higher integrated density compared with that of in-plane exchange bias. PEB devices have been used for spin pinning in magnetoresistance tunneling junction devices. Also owing to the difficult detection of the AFM spin, the spin reversal during PEB has been rarely reported. X-ray magnetic circular dichroism was widely used to detect the surface spin direction of AFM at certain temperature and external magnetic field. [7] However, as discussed later, the antiferromagnetic spin direction at certain temperature and external magnetic field differs for various cooling fields and scanning fields. In addition, there are few reports on the detection of antiferromagnetic spin direction during PEB under continuous changes of temperature and magnetic field.Cr 2 O 3 , an AFM with a Neel temperature (T N ) of 307 K, has two kinds of spin directions þÀþÀ and ÀþÀþ along the c-axis direction of its corundum structure, which can store information of 0 and 1. It has a magnetoelectric effect that can switch its spin directions and work as information writing for a MRAM. Reading can be realized through PEB-coupled ferromagnetic materials (Co...

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supporting

confidence: 51%

mentioning

confidence: 98%

Spin Reversal Mechanism of a Perpendicular Exchange Bias System with an Antiferromagnet Incorporating a Parasitic Ferromagnetism

Shiokawa

Pati

et al. 2019

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“…Anisotropies in the and µ tensors modify the magnitude of B(r) slightly from that of Eqn. (26) (for the case of Cr 2 O 3 using the values from table I we find a difference of 0.05% between the exact solution and that for averaged isotropic and µ), but do not change its monopolar form.…”

Section: Dependence Of the Monopolar Field Strength On The Magnetomentioning

confidence: 75%

Search for the Magnetic Monopole at a Magnetoelectric Surface

et al. 2019

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We show, by solving Maxwell's equations, that an electric charge on the surface of a slab of a linear magnetoelectric material generates an image magnetic monopole below the surface provided that the magnetoelectric has a diagonal component in its magnetoelectric response. The image monopole, in turn, generates an ideal monopolar magnetic field outside of the slab. Using realistic values of the electric-and magnetic-field susceptibilities, we calculate the magnitude of the effect for the prototypical magnetoelectric material Cr 2 O 3 . We use low energy muon spin rotation to measure the strength of the magnetic field generated by charged muons as a function of their distance from the surface of a Cr 2 O 3 film, and show that the results are consistent with the existence of the monopole. We discuss other possible routes to detecting the monopolar field, and show that, while the predicted monopolar field generated by Cr 2 O 3 is above the detection limit for standard magnetic force microscopy, detection of the field using this technique is prevented by surface charging effects. * These authors contributed equally to this work arXiv:1804.07694v3 [cond-mat.mtrl-sci]

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“…Cr 2 O 3 is one of few materials which can achieve 180° manipulation of antiferromagnetic spin in electrical mean. Thus far, electrical manipulation of antiferromagnetic spin in Cr 2 O 3 /FM exchange bias systems has been extensively investigated, for future storage/memory/logic applications . This research has developed detection techniques which access the 180° difference in the antiferromagnetic spin .…”

mentioning

confidence: 99%

“…Figure c,d shows the plot for the scalar product, M Cr2O3 · l , of the Al‐doped and Ir‐doped samples at 50 K against the dopant concentration. Here, we define the antiferromagnetic staggered magnetization vector, l , which is a unit vector representing the direction of the antiferromagnetic domain of Cr 2 O 3 (↑↓↑↓ or ↓↑↓↑ along the z ‐axis in a Cr 2 O 3 unit cell) . The sign of M Cr2O3 · l is determined based on the discussion in the following session.…”

mentioning

confidence: 99%

Manipulation of Antiferromagnetic Spin Using Tunable Parasitic Magnetization in Magnetoelectric Antiferromagnet

Nozaki

Al‐Mahdawi

Shiokawa

et al. 2018

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Antiferromagnets and ferrimagnets with a low net magnetic moment are key components for future spintronic devices because they enable high-integration and high-speed (on the order of THz) operations. Cr 2 O 3 is one of the few antiferromagnets that can achieve 180 manipulation of its spin by electrical means. In this study, the authors developed a new functional material, Cr 2 O 3 , with tunable parasitic magnetization. The authors demonstrate both magnitude and direction tunability of parasitic magnetization in Cr 2 O 3 thin films by doping. A sublattice magnetization reduction and displacement-induced nonequivalent Cr moments by site-selective substitution of nonmagnetic elements are inferred to be the origin of the parasitic magnetization. By utilizing the tunable parasitic magnetization, the authors demonstrate the manipulation of antiferromagnetic single domain. In addition, the authors confirm the low-electric-field switching ability of the antiferromagnetic spin in a doped Cr 2 O 3 /Co exchange coupling system. Such tunable parasitic magnetization enables easy manipulation and detection of antiferromagnetic spin and provides a platform for further understanding of antiferromagnets and research opportunities in innovative spintronics device applications.For a decade, ferromagnetic materials have played a prominent role in the development of spintronics. Ferromagnet (FM)based spintronics have resulted in unique high-performance devices, such as magnetoresistive random-access memory (MRAM). [1] However, specific problems, such as magnetic interferences, are a considerable barrier to further integration of these devices, restricting their future development. One way to overcome such problems is to utilize antiferromagnets (AFMs) or ferrimagnets with low net magnetic moments instead of FMs. As stated by N eel, [2] the high potential of AFMs has been recognized for a long time; AFMs do not generate stray fields, are stable in the presence of an external magnetic field, and have THz precession frequency, which enable the realization of high-integration and ultra-high-speed operation devices. Although the difficulty in conventional manipulation and detection of antiferromagnetic spin restricts its spintronics applications, these processes have increasingly become more feasible due to recent progress. [3][4][5] In particular, 90 control (uniaxial anisotropy control) of antiferromagnetic spin become more feasible. 90 manipulations of the antiferromagnetic spin using an electric current were demonstrated for FeRh through current-induced Joule heating, [6,7] and CuMnAs through spin-orbit torque. [8,9] The corresponding detection techniques, such as anisotropic magnetoresistance (AMR), [8,10,11] tunnel anisotropic magnetoresistance (TAMR), [12] and spin Hall magnetoresistance (SMR) of AFM, [13] which can detect 90 difference in antiferromagnetic spin has also been developed. In contrast, 180 control (unidirectional anisotropy control) of antiferromagnetic spins has been rarely demonstrated, while it enable higher perfo...

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Low-energy magnetoelectric control of domain states in exchange-coupled heterostructures

Cited by 28 publications

References 52 publications

Spin Reversal Mechanism of a Perpendicular Exchange Bias System with an Antiferromagnet Incorporating a Parasitic Ferromagnetism

Spin Reversal Mechanism of a Perpendicular Exchange Bias System with an Antiferromagnet Incorporating a Parasitic Ferromagnetism

Search for the Magnetic Monopole at a Magnetoelectric Surface

Manipulation of Antiferromagnetic Spin Using Tunable Parasitic Magnetization in Magnetoelectric Antiferromagnet

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