Fiber Bragg Grating Dilatometry in Extreme Magnetic Field and Cryogenic Conditions

Abstract

In this work, we review single mode SiO2 fiber Bragg grating techniques for dilatometry studies of small single-crystalline samples in the extreme environments of very high, continuous, and pulsed magnetic fields of up to 150 T and at cryogenic temperatures down to <1 K. Distinct millimeter-long materials are measured as part of the technique development, including metallic, insulating, and radioactive compounds. Experimental strategies are discussed for the observation and analysis of the related thermal expansion and magnetostriction of materials, which can achieve a strain sensitivity (ΔL/L) as low as a few parts in one hundred million (≈10−8). The impact of experimental artifacts, such as those originating in the temperature dependence of the fiber’s index of diffraction, light polarization rotation in magnetic fields, and reduced strain transfer from millimeter-long specimens, is analyzed quantitatively using analytic models available in the literature. We compare the experimental results with model predictions in the small-sample limit, and discuss the uncovered discrepancies.

Enhanced Hybridization Sets the Stage for Electronic Nematicity in CeRhIn5

“…The longitudinal and transverse magnetostriction of CeRhIn 5 was obtained as a function of DC fields to 9 T applied parallel to the aaxis with a resolution in dL/L of 10 −8 . High-field magnetostriction measurements were performed using optical Fiber Bragg Grating (FBG) sensors in a hybrid magnet at 3 He temperatures [19]. The c-axis magnetostriction, dL c /L c , was obtained as a function of DC fields to 45 T applied 20 o off the c-axis.…”

Magnetoelastics of High Field Phenomena in Antiferromagnets UO2 and CeRhIn5

“…The narrow spectral band around 1550 nm that is reflected by the FBG is diverted via a circulator to a 0.5 m spectrometer, where it is spectrally dispersed and detected by an InGaAs line scan camera. The strain sensitivity achieved with this approach is close to one part in 10 million (10 7 ) [13].…”

“…Therefore, dilatometry techniques belong to the basic set of experimental probes present in materials science laboratories. These techniques are used alongside other fundamental magnetic, electric, and thermal capabilities to identify states of matter, to detect classical and quantum phase transitions between different ground states, and to understand the characteristics and nature of such transitions and transformations [13], [14]. Here we use a recently developed optical fiber Bragg grating technique, in continuous and pulsed magnetic fields exceeding 90T, to study magnetoelastic correlations by means of high sensitivity dilatometry at cryogenic temperatures in UO 2 and CeRhIn 5 to better understand their zero field and field-induced lowtemperature states.…”

Note: Optical filter method for high-resolution magnetostriction measurement using fiber Bragg grating under millisecond-pulsed high magnetic fields at cryogenic temperatures

“…However, under pulsed high magnetic fields, the resolution generally gets poorer (∆L/L > 10 −6 ) due to the limited time and space, and noises from mechanical and electrical origin. [3][4][5] FBG is an optical single mode fiber with a Bragg grating at its core with axial length of a few millimeters, enabling us to detect the fine strain ∆L/L of material glued to the FBG fiber. This is achieved by detecting the change in the Bragg wavelength , which is directly proportional to the strain as given by the relation ∆λ B /λ B ∝ ∆L/L.…”

“…FBG based magnetostriction measurement has been reported to be extremely feasible with pulsed high magnetic fields, 3,5-7 owing to the following facts, (a) it is immune to electric noise, (b) the high-quality of the commercially available products, (c) it consumes only small volume and small samples are measurable, and (d) absolute value of strain is obtained directly without calibration.Detection of ∆λ B /λ B depends on high-speed InGaAs spectrometers with broadband light sources in the conventionally reported magnetostriction systems for millisecond-pulsed high magnetic fields. 3,5 The resolution and the speed of the measurement is limited by the specification of the detectors, which is reported to be ∆L/L < 1 × 10 −6 at ∼ 50 kHz. On the other hand, optical filter method has been reported to realize high-speed response of FBG based strain monitor as an a)…”