MAGNETO-OPTIC

Categories: Montana Instruments, Research Platforms

The MAGNETO-OPTIC modules integrate a magnetic field directly into the cryogenic sample chamber. These add-on modules provide the same stability, automation, and control found in all Montana Instruments closed-cycle cryostats.

Compatible accessories and add-ons allow users to configure the instrument for unique experimental requirements, including optional built-in piezo stages for sample motion.

Performance Benefits

Demanding magneto-optic applications are simple to setup, with unique designs to preserve full sample and optical access.
Automatic zero function removes any field stored in the iron poles by using an alternating decreasing field to degauss the poles and effectively eliminate the field when the magnet is off.
Systems include a Hall Probe calibration fixture, power supply, and water cooling for the magnet.

Features

Sample Environment
- Configurable sample space for various experimental requirements
  - Unobstructed sample access – the outer (vacuum) lid, magnet poles, and radiation shield are all removable to make sample setup easy
  - Adjustable sample space – the side “walls” of the radiation shield adjust in the direction of the magnet axis to accomodate various sample mounting configurations and pole tip options (7mm – 20mm spacing)
- Optical access provided from two large side windows, the top, and through bores in the magnet pole axis
  - Overhead microscopy – a recessed objective configuration allows for high NA imagining with a short working distance. The recessed top window insert (left image) provides room for bringing an external objective closer to the sample and modified raised pole tips (center image) bring the magnetic field up to the sample.
  - Magnet bore optical access – 6mm bores through the center of the magnet poles (right image) provide side optical access for incoming and reflected excitation sources.
- Sample mounting and sample motion options available
  - Flexible sample mounting options – various sample mounting schemes are available, including a special electrical sample mount for low voltage DC measurements
  - Sample motion – the platform and sample space can be configured to accommodate integrated XYZ nanopositioning stages for positional control, as well as piezoelectric or manual rotational stages for varying the angle of the sample with respect to the field
Magnet Performance
- Exchangeable pole tips for adjustable field strengths
  - Adjustable field strength – the adjustable radiation shield allows for various pole spacing options down to 12mm (0.7T)
  - Concentrated field strength – special threaded extension pole tips extend through the side aperatures of the radiation shield (with windows removed) to focus the field intensity up to 1T (sample temperature will be ~10K with 5mm pole spacing)
- Hall probe sensor provided for field calibration
  - Accurate field strength – after adjusting the pole tip spacing or sample mounting configuration, the Hall probe fixture calibrates the unit to ensure the maximum field is achieved
- Power Supply and Chiller Unit provide magnet control
  - Precise magnetic field control – a 500W linear bipolar current source with 20 bit resolution allows fine control of the field strength with a 5 µT step size for studying material transitions near zero or in the presence of a strong field
  - Automated software control – current levels are controlled via the standard Cryostation User Interface software and can be automated with external scripting
  - Operational protection – a closed-loop of special coolant keeps the magnet coils from overheating

Specifications

	Cryostation s50 – CO	Notes
PERFORMANCE DATA
Temperature Range	3.4 K – 350 K	w/ radiation shield
Temperature Stability	<10 mk	peak to peak (w/ damped sample mount)
Vibrational Stability	<5 nm	peak to peak
Cool Down Time to 4.2K	~3 hrs
Cooling Power @ Base T	150 mW	measured at sample location
MAGNETIC FIELD
Magnetic Field	0.45 Tesla @ 20mm 0.6 Tesla @ 16mm 0.7 Tesla @ 12mm 1.0 Tesla @ 5mm	distance represents pole tip spacing
Resolution	<5 μTesla	over the full temperature range
Calibration	Hall Probe	Calibration sensor provided
OPTICAL PROPERTIES
Optical Access	5 optical ports	one 50mm top port, two 50mm side ports, two 6mm bores through magnet windings
Working Distance	44.4 mm side window <5 mm top window*	*w/ recessed objective
INTERFACING
Electrical Access	20 user connections¹ 8 configurable¹
Interface Side Panels	1	RF, DC, fiber or gas tube options available
Thermal Lagging	2 locations	to radiation shield
Temperature Sensors	2 Calibrated Cernox™	corresponding to platform and sample temperature -location for 1 user thermometer available
DIMENSIONS
Sample Space	∅7 mm x 23 mm ∅11 mm x 23 mm ∅15 mm x 23 mm	12 mm pole spacing 16mm pole spacing 20 mm pole spacing
Beam Height	100 mm	options available to modify
OPTIONS
Sample Mounting	Magneto-Optic Flange	standard (fixed, adjustable, electrical) & custom alternatives available
Sample Motion	optional nanopositioner integration

Models

The Magneto-Optic module can be added onto existing systems, but it is currently only compatible with the Cryostation s50 platform. For larger chambers or higher magnetic fields, external magnets can be seamlessly integrated through the use of modified housing and castle designs. Learn more.

Cryostation s50 – MO: 0.7 Tesla Bipolar Magnet

A bipolar magnet is integrated directly into the cryogenic sample chamber with fields up to 0.7 Tesla. The unit inserts magnet poles into two of the four standard optical ports, with bores through the magnet cores to allow laser illumination of the sample. The top optical access port can be configured with a recessed objective for low working distance applications.

The field strength depends on the configuration used, with various pole spacing and pole tip options available. An adjustable radiation shield accommodates unique experimental setups, allowing users to expand or resize the sample space or make adjustments to allow for more optical access options.