Abstract

Single negatively-charged nitrogen-vacancy (NV) centers in diamond are stable solid-state single photon sources having an electron spin that can be manipulated via microwaves and read-out via fluorescence measurement [1]. The long relaxation times, on the order of milliseconds even at room temperature, made the center a promising candidate for spin qubit encoding and computing as also nano-magnetometry [2,3] or nanoscale temperature sensing [4]. Therefore, several advances have been made concerning the control of single NV center spins and the understanding of their behaviour in complex environments, as coherent coupling to single surrounding ¹³C nuclei [5], or mechanical manipulation of the defect center electron spin [6]. Progresses have been made also towards the development of an NV based nano-magnetometer, as the implementation of different DC and AC magnetic field measurement protocols [3]. Here, we study the interaction between single NV centers hosted in nanodiamond and single superparamagnetic iron oxide nanoparticles (SPIONs). By combining microwave manipulation of both the NV spin and the particle magnetization, and using AFM techniques to finely control the distance between the two objects, we detect the linear and non-linear response of the SPION single magnetic domain above the Curie temperature. Furthermore, we demonstrate the possibility of using such superparmagnetic nanoparticles as local AC magnetic field amplifiers by driving them with an oscillating field below the blocking frequency – and in the linear regime, allowing hence a more efficient manipulation of the NV center electron spin through the achievement of faster Rabi oscillations. Finally, we discuss the SPION magnetization fluctuations effects on the NV spin dynamics by evaluating the impact on the coherence times involved. With our work, we aim at a better understanding of superparamagnetic nanoparticles behaviour and at their exploitation in integrated magnetic field nanoprobes where several nanostructures are combined to enhance the overall performance of the sensor and extend its potential working range to complex and biological environments.

© 2015 IEEE