Magnetic Field Simulations used for Biological-Sensing with Diamond
Christopher Chen, Mike Gould, Professor Kai-Mei Fu
Introduction
In developing a magnetic sensor, we seek to tag and
optically image biological molecules without
interfering with natural processes. Magnetic field
simulations are required to predict the magnetic
field from test structures designed to characterize
the sensing surface.
ODMR Experimental Data
Simulations using Iron
•
•
𝐵 𝑟 =
1 3𝑟 (𝑚∙𝑟 )
𝑚
− 3
5
4𝜋
𝑟
𝑟
5 𝐴
Magnetization: 1.59 ∙ 10
𝑚
log scale of field
0
-1.4
-1.6
-1.8
1
Nitrogen-Vacancy Center
y (m)
• Nitrogen-vacancy (NV)
centers: defects in diamond
crystal
• One carbon atom replaced
by a nitrogen atom and
another adjacent carbon
atom removed
-2
-2.2
2
B (T)
-2.4
-2.6
-2.8
3
-3
-3.2
-3.4
4
Figure 1: Model of NV center in
diamond lattice [1].
• NV centers used as magnetic sensors due to their
spin properties
0
1
2
x (m)
3
4
Figure 5: z-component magnetic field (T) from cylinder of radius
1 𝜇𝑚 and height of 0.1 𝜇𝑚
Figure 3: ODMR curve taken under a weak DC magnetic field. Blue
crosses are measured data, and red line is a least-squares fit.
log scale of field
0
-1.5
Magnetic Fields
-2
y (m)
• The overlay of varying shapes (cylinder, rectangular
prism,) of magnetic material onto the diamond sample.
• The magnetic field of this material will be determined
by a summation of the magnetic fields from the point
magnetic dipole moments of this material.
• The applied RF will produce a dip in
photoluminescence.
• Magnetic simulations will determine the location of the
magnetic field that is in resonance with the RF field.
1
B (T)
2
-2.5
3
4
-3
-3.5
0
1
2
x (m)
3
4
Figure 6: z-component magnetic field (T) from hollowed cylinder
of outer radius 1 𝜇𝑚, outer radius 0.5 𝜇𝑚 and height 0.1 𝜇𝑚
Conclusion
Figure 2: Energy-level diagram for NV center.
We see fields up to 0.06 T. From prior experimental
results, we can expect a sensitivity down to 2 𝜇𝑇 over a
second. The next step is to create a photoluminescence
map that predicts the experimental image by combining
the simulated magnetic field plot with our experimental
ODMR curve.
ODMR
• Optically-detected magnetic resonance: detection of a
decrease in photoluminescence (PL) when a resonant
radio frequency (RF) magnetic field is applied to the
diamond NV center
• Photoluminescence intensity is dependent on spin state
populations
Figure 4: A magnetic dipole created by magnetic material atop the
diamond sample.
References
[1] Retrieved from
http://www.sci.ccny.cuny.edu/~cmeriles/MagDiamond.htm