Nanoscale magnetometry using quantum mechanical spin; the Nitrogen Vacancy

(NV-) center in diamond

Kapildeb Ambal

National Institute of Standards and Technology, Gaithersburg, Maryland 20899

Institute for Research in Electronics and Applied Physics, University of Maryland, College

Park, MD 20742

Outlines

2

Magnetic Resonance

Electron Spin Resonance (ESR)/Electron Paramagnetic Resonance (EPR)

Optically Detected Magnetic Resonance (ODMR)

Nitrogen Vacancy (NV) Center

Magnetic field sensing using Nitrogen Vacancy (NV-) Center

Spin-wave detection of nano-magnet using Nitrogen Vacancy (NV-) Center

continuous-wave Electron Spin Resonance (cw-ESR)

3

Q

S = 1/2

𝒉𝝂 = 𝒈𝒆𝝁𝐁𝑩𝟎

ms = +1/2

ms = -1/2

Magnetic field

Ener

gy

𝜔𝐿 = − 𝛾𝐵0 = 𝜔0

B1

B0

M0

K. Ambal et al., Phys. Rev. Applied 4, 024008 (2015)

pulsed-Electron Spin Resonance (p-ESR)

4

B0

M0

Laboratory frame Rotating frame

M0B1

M

𝜔1 = − 𝛾𝐵1 𝛼 = −𝛾 𝐵1 𝑡

𝒉𝝂 = 𝒈𝒆𝝁𝐁𝑩𝟎

ms = +1/2

ms = -1/2

Magnetic field

Ener

gyx

y

z

M0

xy

z

B0

𝜔𝐿 = − 𝛾𝐵0

Spin lattice relaxation time (T1 time)

5

M0

Thermal equilibrium

timesi

gnal

B0

𝑀 = 𝑀0 [1 − 2 𝑒−𝑡𝑇1]

M0

Thermal equilibrium

B0B0

M0B1

M

Microwave ON𝜋 pulse

𝛼 = −𝛾 𝐵1 𝑡

B0

Pros and cons of ESR

6

Spectroscopic access of the atomic environment of electron spin

Average distance between spins

Relaxation mechanism

Spin counting

Chemical identity (g factor)

Polarization dependent higher magnetic field better signal

Less sensitive for thin film samples

Expensive equipment needed for the purpose

Minimum of 109 spins are required to get a signal

Optically Detected Magnetic Resonance (ODMR)

7

𝒉𝝂 = 𝒈𝒆𝝁𝐁𝑩𝟎

ms = +1/2

ms = -1/2

Magnetic field

Ener

gyElectro-luminescence Photo-luminescence

Baker et. al, Nat. Comm. 3, 898 (2012).

Why ODMR?

8

Advantages

Highly sensitive Can even detect single spin

Works for thin film devices

Works for low magnetic field

Equipment cost much less

Charge transport dynamics

Charge recombination dynamics

Quantum sensing

Nitrogen Vacancy (NV) center in diamond

9

Atom sized crystal defect

Optically active

Quantum sensing

Works at room temperature

Long coherence time at room temperature A. Haque et al., J. Manuf. Mater. Process 1, 6 (2017)

5.5eV

Ev

Ec

Ground state

Excited state

Formation of Nitrogen Vacancy (NV-) center

10

Nitrogen [N+ ]implantation

Diamond substrate

LatticeVacancy

NV centers

1000 oC

29.5 x103 Counts/s

4.3 x103

Confocal microscopy image

Experimental setup: confocal microscopy

11

Confocal microscopy

B0

cw-ODMR using NV- center

12

532 nm

MW

Read

Quantum sensing; DC magnetometry using NV- center

13

2γB0

Optically detected magnetic resonance (ODMR)

𝐵 =∆𝑓02𝛾

Signal processing for realtime DC magnetometry

14

Modulation

Lockin Amplifier

Quantum measurement Modulated pulse rate Demodulation problem

532 nm

Signal processing; demodulation Concept

15

Modulation

Quantum measurement Modulated pulse rate Demodulation concept

Signal out

K. Ambal et al., US patent 16/519,755 (pending)

cw-ODMR; counter vs ratemeter

16

cw-ODMR: frequency modulated

17

Sensitivity: 4.1 µT/Hz1/2

mod = 500 Hz

K. Ambal et. al., Rev. Sci. Instrum. 90, 023907 (2019)

Continuous magnetometry using NV- center

18

K. Ambal et al., Rev. Sci. Instrum. 90, 023907 (2019).

K. Ambal et al., US patent 16/519,755 (pending)

Realtime magnetometry using NV- center

19

Real-time measurement of magnetic field sweep rate up to 50 µT/s

K. Ambal et. al., Rev. Sci. Instrum. 90, 023907 (2019)

K. Ambal et. al., US patent 16/519,755 (pending)

Pulsed-optically detected magnetic resonance (pODMR)

20

B0

sig

532 nm

MW

Read

Spin lattice relaxation time of NV- center

21

|1⟩Initialize ⟩|0 Readout. . .t

T1 relaxometry

22M. Pelliccione et al., Phys. Rev. Applied 2, 054014 (2014)

equilibriumOptical polarization

|1⟩Initialize ⟩|0 Readout. . .𝜏

M0 M0B1

M

Thermal equilibrium

Microwave ON𝜋 pulse𝛼 = −𝛾 𝐵1 𝑡

Magnetism

23

Medical imagining

Vehicle brakingInformation storage

Advances in magnetism

24

Capacity: 5 MB or 1 songCapacity: 4 TB or 800,000 songs

1956, IBM2016, Seagate

Future of magnetic technology

25

Magnetic Random Access memory

Nonvolatile: Holds data in the event

of a power outage

Magnetic memory will be small, fast,

numerous.

Magnetic random access memory (MRAM)

26

“0”“1”

Free layer

Barrier layer

Fixed layer

Magnetic tunnel junction (MTJ)

Static and dynamic properties of “free layer” determine device properties

Static properties:CoercivityExchange

Dynamic properties:Spin wave modesFerromagnetic resonance

Thermal spin wave modes

27

Bapp

T1 relaxometry spin wave mode detection

28

1

𝑇1=

1

𝑇10 +

𝛾2

2⟨𝑆𝐵𝑥 + 𝑆𝐵𝑦⟩

Spectral density [T2/Hz]

Bapp

Conclusions

29

Realtime DC magnetometry using quantum sensor

Magnetic noise spectroscopy of nanomagnet

Acknowledgement

30

Robert D. McMichael

Sergey Dushenko

Cooperative Research Agreement # 70NANB14H209

Questions

31