Interface-induced magnetic coupling in multiferroic/ferromagnetic bilayer: An ultrafast pump-probe study

La-o-vorakiat, Chan; Tian, Yuan; Wu, Tom; Panagopoulos, C.; Zhu, Jian‐Xin; Su, Haibin; Chia, Elbert E. M.

doi:10.1063/1.4870580

Cited by 7 publications

(4 citation statements)

References 29 publications

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“…In conclusion, we have presented the foremost example of exchange-bias particle presented in this study constitute a striking illustration of how a subtle combination of interactions may permit the occurrence of unique magnetic properties by exploiting proximity effects in magnetism. A similar approach could be applied to other composite systems, in and beyond magnetism, where proximity effects may be engineered to enhance material's functionality [30,[60][61][62][63][64].…”

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confidence: 99%

High Temperature Magnetic Stabilization of Cobalt Nanoparticles by an Antiferromagnetic Proximity Effect

et al. 2015

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Thermal activation tends to destroy the magnetic stability of small magnetic nanoparticles, with crucial implications in ultra-high density recording among other applications. Here we demonstrate that low blocking temperature ferromagnetic (FM) Co nanoparticles (T B <70 K) become magnetically stable above 400 K when embedded in a high Néel temperature antiferromagnetic (AFM) NiO matrix. The origin of this remarkable T B enhancement is due to a magnetic proximity effect between a thin CoO shell (with low Néel temperature, T N ; and high anisotropy, K AFM ) surrounding the Co nanoparticles and the NiO matrix (with high T N but low K AFM ). This proximity effect yields an effective AFM with an apparent T N beyond that of bulk CoO, and an enhanced anisotropy compared to NiO. In turn, the Co core FM moment is stabilized against thermal fluctuations via core-shell exchange-bias coupling, leading to the observed T B increase. Mean-field calculations provide a semi-quantitative understanding of this magnetic-proximity stabilization mechanism. 2The current miniaturization trend in magnetic applications has led to a quest to suppress spontaneous thermal fluctuations (superparamagnetism) in ever-smaller nanostructures [1][2][3][4][5], which is a clear example of the fundamental efforts of condensed matter physics to meet technological challenges [6] (e.g., the continued growth of recording density [7]). Despite the foreseeable change of recording paradigm from continuous to patterned media, where each bit is recorded in an individual nanostructure [7], the key for sustained storage density increase will remain the introduction of progressively more anisotropic (high K) materials [8], which allow for magnetic stability at very small volumes, V (i.e., blocking temperature, T B ∝ KV, above room temperature, RT). Two main strategies are largely investigated to achieve high K (both of them with implications in other active technologies beyond information storage, such as permanent magnets, magnetic hyperthermia or even sensors [5,[9][10][11]): (i) the use of compounds with intrinsically high magnetocrystalline anisotropy (such as FePt [3,8]) and (ii) the design of exchange-coupled nanocomposites [4,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].Unfortunately, most high-K materials require high-temperature annealing processes to obtain the desired phase, which could hamper their implementation in certain structures. Thus, FM-AFM exchange coupling alternatives may be an appealing option. In fact, it has been demonstrated [4] that ferromagnetic-antiferromagnetic (FM-AFM) interfacial exchangecoupling is an effective method, later patented by Seagate [12], to increase the effective K of FM nanoparticles. However, a T B enhancement beyond RT using this approach has been rarely reported [22][23][24][25][26] (where often broad particle size distribution can partly account for the "apparent" T B increase [22][23][24][25]). The reason for this scarcity is that high Néel temperature (T N ) AFMs tend to h...

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High Temperature Magnetic Stabilization of Cobalt Nanoparticles by an Antiferromagnetic Proximity Effect

et al. 2015

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“…Ultrafast optical measurements have been proven to be highly reliable in understanding the timescale and role of photoexcitation in these phase transitions 3 . The study of time-dependent carrier dynamics has helped in understanding the contributions of charge, spin, and lattice degrees of freedom to phase transitions in complex oxides 4 5 6 7 . Recent efforts on time-resolved optical measurements have significantly advanced efforts on optical control of MIT in complex oxides, and have gained a lot of interest particularly owing to its promise of realizing ultra high-speed opto-electronic devices 4 8 .…”

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Evidence for Photoinduced Insulator-to-Metal transition in B-phase vanadium dioxide

Lourembam

Srivastava

La-o-vorakiat

et al. 2016

Sci Rep

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Ultrafast optical studies have been performed on epitaxial films of the novel B-phase of vanadium dioxide using temperature-dependent optical pump-probe technique. Signature of temperature-driven metal-to-insulator transition was distinctly observed in the ultrafast dynamics — the insulating phase showed two characteristic electronic relaxation times while the metallic phase showed only one. Beyond a threshold value of the pump fluence, the insulating state collapses into a ‘metallic-like’ phase which can be further subdivided into two regimes according to the lengths of the fast characteristic time. The first regime can be explained by lattice heating due to the optical pump; the other cannot be accounted by simple lattice heating effects alone, and thus offers evidence for a true photoinduced phase transition.

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“…The spin dynamics are activated by heating up T LAF and T CAF . We propose a three-reservoir model, incorporating three degrees of freedom, lattice (L), LAF order and CAF order, to describe the temperature dynamics, as follows [26]:…”

Section: Resultsmentioning

confidence: 99%

Magnetic phase transition in DyFe _0.6 Mn _0.4 O ₃ crystal investigated with ultrafast spectroscopy

Pan

Zhang

Jin

et al. 2015

EPL

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By use of optical pump-probe spectroscopy, we report the ultrafast carrier dynamics in a DyFe0.6Mn0.4O3 (DFMO) single crystal. We find that the photo-excited electrons firstly relax through a fast electron-phonon coupling , followed by intermediate relaxation (tens of ps) and slow nanosecond relaxation processes. Meanwhile, a photo-induced coherent acoustic phonon with frequency of 36.3 GHz is detected, and the sound velocity with magnitude of is determined. Moreover, the time constants in intermediate relaxation are found to increase significantly in the vicinity of the Morin-like phase transition temperature and the Néel temperature, which are interpreted as the coexisting of collinear- and canted-antiferromagnetic properties in DFMO, and the spectroscopic results are consistent with the temperature-dependent magnetic-moment measurements.

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Interface-induced magnetic coupling in multiferroic/ferromagnetic bilayer: An ultrafast pump-probe study

Abstract: Interface-induced magnetic coupling in multiferroic/ferromagnetic bilayer: An ultrafast pump-probe study. Applied Physics Letters, 104( 14), 141602-.

Cited by 7 publications

References 29 publications

High Temperature Magnetic Stabilization of Cobalt Nanoparticles by an Antiferromagnetic Proximity Effect

High Temperature Magnetic Stabilization of Cobalt Nanoparticles by an Antiferromagnetic Proximity Effect

Evidence for Photoinduced Insulator-to-Metal transition in B-phase vanadium dioxide

Magnetic phase transition in DyFe _0.6 Mn _0.4 O ₃ crystal investigated with ultrafast spectroscopy

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Interface-induced magnetic coupling in multiferroic/ferromagnetic bilayer: An ultrafast pump-probe study

Abstract: Interface-induced magnetic coupling in multiferroic/ferromagnetic bilayer: An ultrafast pump-probe study. Applied Physics Letters, 104( 14), 141602-.

Cited by 7 publications

References 29 publications

High Temperature Magnetic Stabilization of Cobalt Nanoparticles by an Antiferromagnetic Proximity Effect

High Temperature Magnetic Stabilization of Cobalt Nanoparticles by an Antiferromagnetic Proximity Effect

Evidence for Photoinduced Insulator-to-Metal transition in B-phase vanadium dioxide

Magnetic phase transition in DyFe 0.6 Mn 0.4 O 3 crystal investigated with ultrafast spectroscopy

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Product

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Magnetic phase transition in DyFe _0.6 Mn _0.4 O ₃ crystal investigated with ultrafast spectroscopy