A magnon scattering platform

At a Glance

Metadata	Details
Publication Date	2021-06-15
Journal	Proceedings of the National Academy of Sciences
Authors	Tony Zhou, Joris J. Carmiggelt, Lisa Maria Gächter, Ilya Esterlis, Dries Sels
Institutions	New York University, ETH Zurich
Citations	53
Analysis	Full AI Review Included

Technical Documentation & Analysis: Magnon Scattering Platform

This document analyzes the research paper “A Magnon Scattering Platform” to highlight the critical role of high-quality Single Crystal Diamond (SCD) and related fabrication services offered by 6CCVD.

Executive Summary

The research successfully demonstrates a novel, table-top platform for studying the magnetic properties of mesoscopic materials using coherent magnonic (spin wave) scattering, leveraging the unique capabilities of the Nitrogen Vacancy (NV) center in diamond.

Core Achievement: Demonstrated the first 2D table-top scattering platform capable of spatially resolving both the amplitude and phase of scattered magnonic waves.
Critical Component: The platform relies entirely on a single NV center embedded in Single Crystal Diamond (SCD), functioning as a high-resolution, nanometer-scale magnetometer.
Resolution & Sensitivity: Achieved sub-wavelength imaging, resolving magnons with wavelengths down to 660 nm, enabling the extraction of target material properties (e.g., saturation magnetization $M_{S}$).
Material System: Magnons were generated in a 100 nm Yttrium Iron Garnet (YIG) film and scattered off a 5 µm diameter Permalloy (Py) disk target.
Methodology: Phase detection was achieved using an interference scheme, combining the local magnon field with a uniform RF reference field, confirming the coherent nature of the scattering process.
Future Applications: The platform is established as a powerful tool for studying correlated many-body systems, including interactions with superconductors and topological insulators.
6CCVD Value Proposition: This research validates the need for high-purity, crystallographically controlled SCD substrates, a core specialization of 6CCVD, for advanced quantum sensing applications.

Technical Specifications

The following hard data points were extracted from the experimental setup and results:

Parameter	Value	Unit	Context
Detector Material	Single NV Center	N/A	Embedded in diamond scanning probe.
NV Ground State Splitting	2.87	GHz	At zero magnetic field.
YIG Film Thickness	100	nm	Magnon propagation medium.
Target Material	Permalloy (Py) Disk	N/A	Deposited on YIG surface.
Target Thickness	100	nm	Py disk thickness.
Target Diameter	5	µm	Py disk diameter.
Magnon Drive Frequency	2.18 to 2.3	GHz	Used for coherent excitation.
External Magnetic Field (B_ext)	132	G	Used to tune NV ESR frequency.
Shortest Magnon Wavelength Detected	640	nm	Limited by stripline design efficiency.
Magnon Wavelength Resolved	660	nm	Easily resolved in fluorescence phase maps.
Fitted Saturation Magnetization (M_S)	1946	G	Extracted from Damon-Eshbach dispersion fit.
Measured Scattering Cone Angle ($\theta_{c}$)	28 ± 2	°	Observed at 2.18 GHz.
NV Axis Orientation	35.26	°	Tilted out of plane relative to the stripline.

Key Methodologies

The experiment relies on precise material engineering and quantum control to achieve nanometer-scale magnetic field sensing:

Substrate and Film Growth: A 100 nm thin film of Yttrium Iron Garnet (YIG) was grown on a Gadolinium Gallium Garnet (GGG) substrate to serve as the “vacuum” supporting long-lived, coherent magnonic excitations (Damon-Eshbach Surface Waves, DESW).
Source Fabrication: A micro stripline was deposited onto the YIG surface. Driving a microwave current through this stripline launched magnons with a k-vector perpendicular to the current direction.
Target Fabrication: A 100 nm thick, 5 µm diameter Permalloy (Py) disk was deposited directly onto the YIG surface to act as the magnetic scattering target.
NV Center Sensing: A single Nitrogen Vacancy (NV) center in a diamond tip was used as a scanning probe magnetometer. The NV Electron Spin Resonance (ESR) frequency was tuned via an external magnetic field ($B_{ext}$) to match the magnon frequency.
Phase Measurement: An interference scheme was implemented by applying a uniform RF reference field ($B_{ref}$) alongside the local magnon field ($B_{magnon}$). Scanning the NV probe measured the resulting fluorescence modulation, which is proportional to the amplitude and phase difference between the two fields.
Dispersion Extraction: By varying the phase difference of the microwave sources and measuring the resulting interference pattern, the real-space propagating component of the magnons was captured, allowing direct extraction of the magnon dispersion relation down to 640 nm wavelengths.

6CCVD Solutions & Capabilities

This research underscores the necessity of ultra-high-quality, custom-engineered diamond materials for next-generation quantum sensing and spintronics. 6CCVD is uniquely positioned to supply the materials and fabrication services required to replicate and advance this platform.

Applicable Materials

Research Requirement	6CCVD Material Recommendation	Technical Rationale
High-Coherence NV Host	Optical Grade Single Crystal Diamond (SCD)	Provides the lowest defect density and highest purity necessary for maximizing NV spin coherence time ($T_{2}$), crucial for sensitive magnetometry and Rabi oscillation detection.
Advanced Sensing Probes	Custom SCD Plates/Wafers	SCD material supplied in custom dimensions (down to 0.1 µm thickness) for integration into scanning probe tips (AFM/NV) requiring nanometer precision.
Future Conductive Targets	Heavy Boron-Doped Diamond (BDD)	For extending the platform to study interactions with superconductors or topological insulators, BDD offers a highly conductive, inert, and robust electrode material.

Customization Potential

The complexity of the magnon scattering platform demands precise material control and advanced processing, all available in-house at 6CCVD:

Crystallographic Orientation Control: The experiment required the NV axis to be oriented 35.26° out of plane. 6CCVD specializes in MPCVD growth of SCD along specific, non-standard crystallographic directions, ensuring optimal alignment for maximum coupling efficiency between the NV spin and the magnetic field.
Custom Dimensions and Polishing: We provide SCD plates and wafers up to 500 µm thick, polished to an ultra-smooth finish (Ra < 1 nm). This surface quality is essential for minimizing strain and ensuring high-fidelity deposition of subsequent layers (YIG, Py targets, striplines).
Integrated Metalization Services: The platform requires precise microwave striplines and reference antennas. 6CCVD offers internal metalization capabilities (Au, Pt, Ti, Cu, W) for depositing high-conductivity, low-loss microwave circuits directly onto the diamond substrate or probe components.
Laser Cutting and Shaping: We offer precision laser cutting services to shape the SCD into the specific geometries required for scanning probes or integrated microwave cavities, ensuring compatibility with conventional AFM technology (Ref. 12).

Engineering Support

6CCVD’s in-house PhD team provides expert consultation on material selection and integration for complex quantum projects. We can assist researchers in optimizing diamond specifications—including nitrogen concentration, isotopic purity, and surface termination—to maximize NV center performance for similar Magnon Scattering and Quantum Magnetometry projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Significance This work describes a general scattering platform that uses magnons to explore the underlying properties of target materials. In this work we show how both phase and amplitude of magnons can be imaged using a nitrogen vacancy center magnetometer and how the scattered pattern of waves can be used to infer geometric and magnetic properties of a target material. To demonstrate this new experimental methodology we use a permalloy disk as our target and show that even with such a simple target unexpected behavior is observed. In addition, we provide a theoretical framework to reconstruct the properties of the target.