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A high-amplitude microwave magnetic field localized at the nanoscale is a desirable tool for various applications within the rapidly developing field of nanomagnetism. Here, we drive magnetization precession by coherent phonons in a metal ferromagnetic nanograting and generate ac-magnetic induction with extremely high amplitude (up to 10 mT) and nanometer scale localization in the grating grooves. We trigger the magnetization by a laser pulse which excites localized surface acoustic waves. The developed technique has prospective uses in several areas of research and technology, including spatially resolved access to spin states for quantum technologies.The exploration of magnetism at the nanoscale continues to be a rapidly developing field. Magnetic recording with ultrahigh densities [1] for data storage, magnetic resonant imaging with nanometer resolution [2, 3] for medicine and biology, addressing the magnetic states of atoms [4][5][6][7][8] for quantum computing, and ultrasensitive magnetic sensing [9] are the most prominent examples within the multifaceted research field of nanomagnetism. Most of the proposed concepts and prototypes utilize oscillating (ac-) magnetic fields with frequencies from millions up to hundreds of billions of cycles per second (10 6 -10 11 Hz). The oscillating magnetic fields are used to override the coercivity of ferromagnetic grains [10], to set atomic magnetic moments to a desired state [2,3,9], and to encode quantum information into spin states [4][5][6][7][8]11]. These examples utilize conventional methods for the generation of ac-magnetic fields: an external rf-generator in combination with a microwire [2][3][4][5][9][10][11] or a microwave cavity [6][7][8]11]. This methodology cannot be applied at the nanometer scale. A key breakthrough would be nanoscale generation of high-amplitude, monochromatic ac-magnetic fields. This would open the possibility to address neighboring nano-objects, e.g. spin qubits, independently, and to reduce the energy consumption in magnetic devices. It is however a challenging task to reach this goal because current technologies do not allow one to control the frequency, bandwidth and amplitude of an ac-magnetic field on the nanoscale.An efficient way to generate a high-frequency ac magnetic field is to induce coherent magnetization precession in a ferromagnet. The magnetization of ferromagnetic metals may be as large as 2 T. Precessional motion with frequencies of 10 GHz allows the generation of highamplitude microwave magnetic fields on the picosecond time scale. The magnetization precession can be driven by dc-spin polarized currents [12]. This approach is realized in microwave generators based on spin torque nanooscillators, but has severe limitations, e.g. in combining large amplitudes and high frequencies [13]. Coherent phonons, bulk [14,15] or surface [16,17] acoustic waves, have been successfully used for exciting the magnetization precession in ferromagnetic films. The effect of a surface acoustic wave (SAW) on the magnetic order in a ferromag...

The influence of both bulk and edge pinning on the response of a thin-film superconductor to an oscillating magnetic field is considered. The magnetic-flux-defreezing field and the flux-exit field are defined. The hysteresis and magnetization curves of a sample are constructed for the entire cycle of the magnetic field. From this, we obtain the dependence of the hysteresis losses on the field amplitude.

Recent theoretical and experimental research on low-bulk-pinning superconducting strips has revealed striking dome-like magnetic-field distributions due to geometrical edge barriers. The observed magnetic-flux profiles differ strongly from those in strips in which bulk pinning is dominant. In this paper we theoretically describe the current and field distributions of a superconducting strip under the combined influence of both a geometrical edge barrier and bulk pinning at the strip's critical current Ic, where a longitudinal voltage first appears. We calculate Ic and find its dependence upon a perpendicular applied magnetic field Ha. The behavior is governed by a parameter p, defined as the ratio of the bulk-pinning critical current Ip to the geometrical-barrier critical current Is0. We find that when p > 2/π and Ip is field-independent, Ic vs Ha exhibits a plateau for small Ha, followed by the dependence Ic − Ip ∝ H −1 a in higher magnetic fields.The combination of a geometrical edge barrier and bulk pinning recently has been shown to strongly affect the properties of low-dimensional superconductors (thin films, single crystals, and tapes with high demagnetizing factors) placed in either a perpendicular magnetic field 1-5 or a transport-current-carrying state 6-9 . While most experimental studies of the field dependence of the critical current I c are being interpreted solely on the basis of bulk-pinning theory (see for example 10-14 ), a number of works 6,8,15,16 have shown that a geometrical edge barrier (or surface barrier) may strongly affect I c . In this paper we study the combined effect of a geometrical edge barrier and bulk pinning upon the magnetic field dependence of I c for type-II superconducting strips. We shall show how the dependence of I c upon H a is controlled by the parameter p = I p /I s0 , where I p is the bulk-pinning critical current in the absence of a geometrical edge barrier, and I s0 is the geometrical-barrier critical current in the absence of bulk pinning.We consider a superconducting strip of thickness d (|y| < d/2) and width 2W (|x| < W ) centered on the z axis. We assume that d is less than the London penetration depth λ and that W is much larger than the two-dimensional screening length Λ = 2λ 2 /d. The strip is subjected to a perpendicular applied magnetic field H a = (0, H a , 0), and it carries a total current I in the z direction described by a spatially dependent sheet current density K(x) = Jd = [0, 0, K z (x)]. We wish to determine the current-density and magnetic-field distributions at the critical current at which a steady-state flux-flow voltage appears along the length of the strip. For a strip containing no magnetic flux, K z (x) is the sum of two contributions,

We theoretically analyze exciton-photon oscillatory dynamics within a homogenous polariton gas in the presence of energy detuning between the cavity and quantum well modes. Whereas pure Rabi oscillations consist of the particle exchange between the photon and exciton states in the polariton system without any oscillations of the phases of the two subcondensates, we demonstrate that any nonzero detuning results in oscillations of the relative phase of the photon and exciton macroscopic wave functions. Different initial conditions reveal a variety of behaviors of the relative phase between the two condensates, and a crossover from Rabi-like to Josephson-like oscillations is predicted.