Ultrasensitive mechanical detection of magnetic moment using a commercial disk drive write head

Abstract

Sensitive detection of weak magnetic moments is an essential capability in many areas of nanoscale science and technology, including nanomagnetism, quantum readout of spins and nanoscale magnetic resonance imaging. Here we show that the write head of a commercial hard drive may enable significant advances in nanoscale spin detection. By approaching a sharp diamond tip to within 5 nm from a write pole and measuring the induced diamagnetic moment with a nanomechanical force transducer, we demonstrate a spin sensitivity of 0.032 μB Hz−1/2, equivalent to 21 proton magnetic moments. The high sensitivity is enabled in part by the pole's strong magnetic gradient of up to 28 × 106 T m−1 and in part by the absence of non-contact friction due to the extremely flat writer surface. In addition, we demonstrate quantitative imaging of the pole field with ∼10 nm spatial resolution. We foresee diverse applications for write heads in experimental condensed matter physics, especially in spintronics, ultrafast spin manipulation and mesoscopic physics.

Spin-Mechanical Scheme with Color Centers in Hexagonal Boron Nitride Membranes

“…Here, the fundamental vibrational mode of a circularly clamped monolayer hBN membrane with radius R with a dominant built-in tensile strain is taken as the mechanical mode [15,19]. Here we consider a maximum magnetic field gradient of |∂ z B ⊥ (r 0 , θ 0 , 0)| ≈ 270 G/nm at 'sweet spot' r 0 = (r 0 , θ 0 ), which can be provided either by a write-head [27,30] or a slightly enhanced magnetic tip [24]. Remarkably, the maximum spin-motion coupling rate g 0 ≡ g(r 0 , θ 0 ) can become comparable or even larger than the oscillator frequency ω m , hence the so-called ultrastrong coupling regime can be achieved [ Fig.…”

Growth of magnetic nanowires along freely selectable 〈hkl〉 crystal directions

“…This system has the highest reported saturation magnetization at room temperature among all thermodynamically stable alloys ( , ref. 30 ), and is the material of choice for applications where a high magnetic moment is required 14 , 16 – 18 , 31 . To initiate our process, we first established the conditions for growing biaxial FeCo films using only Source 1 (see Supplementary Note 1 , Supplementary Methods: Section 5.7).…”

Generating spin squeezing states and Greenberger-Horne-Zeilinger entanglement using a hybrid phonon-spin ensemble in diamond

“…The NV centers can be arranged as an array with precise position in an ultrathin film of diamond [55][56][57] . A large magnetic field gradient up to 4 × 10 7 T/m has been reported in the magnetic disk drive system 58,59 . In magnetic resonance force microscopy systems, the gradient larger than 10 6 T/m has been realized [60][61][62][63] .…”