Single Spin Magnetometry at the Nansocale

Since the discovery of ferromagnetism in 2D van der Waals crystals, the community aims to study the feature quantitatively at the nanoscale. This feat was now approached by the group of Patrick Maletinsky at the University of Basel (Basel, CH).
Using their single-spin magnetometer based on electronic spins in diamond with the attoAFM/CFM, they detected the magnetization distribution of atomically thin crystals of CrI3. attocube's attoAFM/CFM offers the possibility to combine atomic force with confocal microscopy for optically detected magnetic resonance. With their technique they found the magnetization of one monolayer to be ≈ 16 µB/nm2 and addressed an open question regarding the thickness-dependence of magnetisation in CrI3.
Next to the outstanding physical result it is the technique that will add new ways of detecting and manipulating of magnetic properties at the nanoscale. According to P. Maletinsky the "single-spin magnetometry" is a "close-to ideal tool to study the physics of atomically thin 2D magnets."

This measurement was realized with the attoAFM/CFM.

Single Spin Magnetometry at the Nansocale AFM CFM  attoLIQUID
Single Spin Magnetometry at the Nansocale AFM CFM  attoLIQUID

Nanoscale Imaging and Control of Domain Wall Hopping with an NV Center Microscope attoLIQUID  attoAFM CFM oder CSFM

Nanoscale Imaging and Control of Domain-Wall Hopping with an NV Center Microscope

Domain walls in magnetic wires may prove useful for future spintronic devices, and hence their nanoscale characterization is an important steps towards useful applications. As demonstrated by the group of Vincent Jaques in Science, their NV center microscope based on the attoAFM/CFM allows to image domain walls in a 1 nm thick ferromagnetic nanowire with high resolution as well as jumps between pinning sites of individual domain walls. At the same time, they showed that the domain walls can be moved along the wire by inducing jumps via local heating due to a high local laser power. Since the domain walls are pinned by nearest pinning site, this allows to probe and image the pinning landscape of the sample quite efficiently.

(Images courtesy of V. Jacques, University of Montpellier, FR)

This measurement was realized with the attoLIQUID1000, and the attoAFM/CFM.


Optical Magnetometer Reveals Lack of Conventional Meissner Effect in Iron based Superconductors attoLIQUID  attoAFM CFM oder CSFM

Optical Magnetometer Reveals Lack of Conventional Meissner Effect in Iron-based Superconductors

Scientists at Ames Laboratory (US), Ruslan Prozorov and Naufer Nusran, together with graduate student Kamal Joshi succeeded to visualize spatial distribution of the magnetic induction upon penetration and expulsion of weak magnetic fields in several representative superconductors. The experimental setup is based on the Attocube AFM/CFM, a low-temperature AFM combined with a confocal microscope. Attocube’s  high NA low temperature microscope objective is used to optically access the nitrogen-vacancy centers in diamond, which are essentially atomic-scale magnetic sensors.

This measurement was realized with the attoLIQUID1000, and the attoAFM/CFM.


NV-Center Based Nanomagnetometry

Given its premier mechanical and thermal stability, the attoAFM/CFM is the ideal platform for nanoscale magnetic imaging employing an AFM tip with a diamond nanocrystal that contains a single nitrogen-vacancy (NV) center [1]-[4]. Local magnetic fields are subsequently evaluated by measuring the Zeeman shifts of the NV defect spin sublevels. In the particular case of NV-center magnetometry, an external microwave field is emitted and tuned in frequency such that local spin resonance occurs. This condition can subsequently be detected by a decrease in photoluminescence intensity of the NV-center, referred to as ODMR (optically detected magnetic resonance). Using a Lock-in and feedback loop technique allows to maintain spin resonance while rastering the sample, allowing to record a local magnetic field map with nanometer resolution.
In this example, magnetic imaging of a hard disk sample with random bit orientation was performed in the group of V. Jacques at LPQM, ENS-Cachan, France. [1]
Example 1 (a,b): Quantitative imaging using ODMR based method with NV-center scanned at d1 = 250 nm above the sample. (a) Schematic of the measurement. (b) Quantitative magnetic field distribution recorded with the lockin technique (13 nm pixel size, 110 ms acquisition time per pixel). The inset shows a line-cut taken along the dashed white line in the image. [1]
Example 2 (c,d): All-optical method with NV center closer to the sample surface. (c) Schematic of the measurement. (d) All optical photoluminescence image (no microwave field applied) recorded with the NV-scanning probe magnetometer in tapping mode (8 nm pixel size, 20 ms acquisition time per pixel). Comparisons with simulations indicates that the tip surface distance is roughly d2 = 30 nm. Fine white dotted lines are plotted along the direction of the hard disk tracks as a guide for the eye. [1]

Related publications based on the attoAFM/CFM (2012-2016)
[5] A. Dréau et al., Phys. Rev. Lett. 113, 137601 (2014)
[6] A. Dréau et al., Phys. Rev. Lett. 110, 060502 (2013)
[7] L. Rondin et al., Nature communications 4, 2279 (2013)
[8] J.-P. Tetienne et al., Phys. Rev. B 87, 235436 (2013)
[9] J.-P. Tetienne et al., New J. Phys. 14, 103033 (2012)
[10] A. Dréau et al., Phys. Rev. B 85, 134107 (2012)
[11] L. Rondin et al., Appl. Phys. Lett. 100, 153118 (2012)

This measurement was realized with the attoLIQUID1000, and the attoAFM/CFM.

NV Center Based Nanomagnetometry attoLIQUID  attoAFM CFM oder CSFM
NV Center Based Nanomagnetometry attoLIQUID  attoAFM CFM oder CSFM
NV Center Based Nanomagnetometry attoLIQUID  attoAFM CFM oder CSFM
NV Center Based Nanomagnetometry attoLIQUID  attoAFM CFM oder CSFM

Quantitative Nanoscale Vortex-Imaging of Superconductors

Understanding the microscopic mechanisms of superconductivity could be greatly facilitated by non-invasive tools that allow for quantitative imaging with nanometric resolution over a large range of temperatures and high magnetic fields. Based on the attoAFM/CFM, the group of Patrick Maletinsky (Univ. of Basel) reports on cryogenic measurements using NV center magnetometry. Their technique allows to extract quantitative data on the local magnetic field of individual superconducting vortices in YBCO with high sensitivity and spatial resolution. By determining the local London penetration depth, they find that the so called Pearl-vortex model explains the data much better and allows for fitting of additional parameters than the standard monopole model. Their experiments constitute an impressive example for how far the practical use of the NV center based magnetometry tools has already evolved.

(Images courtesy of P. Maletinsky, University of Basel, CH)

This measurement was realized with the attoLIQUID1000, and the attoAFM/CFM.

Quantitative Nanoscale Vortex Imaging of Superconductors attoAFM CFM oder CSFM  attoLIQUID
Quantitative Nanoscale Vortex Imaging of Superconductors attoAFM CFM oder CSFM  attoLIQUID
Quantitative Nanoscale Vortex Imaging of Superconductors attoAFM CFM oder CSFM  attoLIQUID

attoAFM CFM in Toploading Insert attoAFM CFM oder CSFM  mK

attoAFM/CFM in Toploading Insert

The presented data was taken with a mk-compatible version of the attoAFM/CFM mounted on a toploading insert of a Leiden Cryogenics closed-cycle dilution refrigerator. The sample temperature was 60 mK during an AFM scan with a speed of 400nm/s. The images nicely demonstrates that the delicate microscope works very well even under these extreme conditions.

This measurement was realized with the attoAFM/CFM.