Anisotropy Of Susceptibility Research Articles

Formation and Control of Twin Domains in the Pyrochlore Oxide Cd2Re2O7

The successive phase transitions of the pyrochlore oxide Cd2Re2O7 are studied by polarizing microscopy and magnetic susceptibility measurements. The formation of twin domains is visualized in the polarizing images of a pristine (111) crystal surface upon cooling through the cubic-to-tetragonal transition at Ts1 ∼ 200 K. Moreover, a dramatic change in the twinning pattern is observed at Ts2 ∼ 120 K, which suggests that the tetragonal c-axis flips as the strain changes its direction at the tetragonal-to-tetragonal transition. Magnetic susceptibility measurements reveal significant domain alignment upon cooling across Ts1 and Ts2 in a magnetic field of 7 T, which are due to ∼10% anisotropy in the magnetic susceptibility for the low-temperature phases. Interestingly, the anisotropy is reversed at Ts2: χc < χa above Ts2 and vice versa below Ts2.

Uniaxial Diffusional Narrowing of NMR Lineshapes for Membrane Proteins Reconstituted in Magnetically Aligned Bicelles and Macrodiscs

Structure and dynamics of membrane proteins can be effectively studied by oriented-sample solid-state nuclear magnetic resonance (NMR) techniques when the lipid bilayers are macroscopically aligned with respect to the main magnetic field. Magnetic alignment of the protein-containing membrane bilayer results from the negative susceptibility anisotropy of the lipid hydrocarbon interior yielding perpendicular sample alignment. At this orientation, while the uniformity of alignment represents an essential prerequisite for obtaining high-quality NMR spectra, further line narrowing is obtained by uniaxial motional averaging of the azimuthal parts of the chemical shift anisotropies and dipolar couplings. The motional averaging is brought about by uniaxial rotational diffusion of the protein molecules about the normal to the membrane surface, which is perpendicular to the magnetic field. Uniaxial averaging is efficient when the motion about the axis of alignment becomes sufficiently fast (on the timescale of the dipolar couplings and chemical shift anisotropies). Line narrowing under uniaxial rotation can be theoretically modeled using the stochastic Liouville equation. In this mini-review, we illustrate the method of uniaxial averaging for the relatively small Pf1 coat protein which exhibits excellent resolution in magnetically aligned bicelles due to its fast uniaxial diffusion and even superior resolution in large (30 nm) nanodiscs (macrodiscs) stabilized by a belt peptide. Spectra of Pf1 coat protein in polymer-stabilized macrodiscs, an alternative and more robust alignment media, are presented. We also report on preliminary spectra of a much larger protein—uniformly 15N labeled M1-M4 domain for the human acetylcholine receptor. While some spectral resolution is apparent, significantly broader linewidths emphasize the need for creating fast rotating discoidal membrane mimetics.

Determining the local low-energy excitations in the Kondo semimetalCeRu4Sn6using resonant inelastic x-ray scattering

We have investigated the local low-energy excitations in CeRu$_4$Sn$_6$, a material discussed recently in the framework of strongly correlated Weyl semimetals, by means of Ce $M_5$ resonant inelastic x-ray scattering (RIXS). The availability of both $^2$F$_\frac{5}{2}$ and $^2$F$_\frac{7}{2}$ excitations of the Ce $4f^1$ configuration in the spectra allows for the determination of the crystal-electric field parameters that explain quantitatively the temperature dependence and anisotropy of the magnetic susceptibility. The absence of an azimuthal dependence in the spectra indicates that all crystal-electric field states are close to being rotational symmetric. We show further that the non-negligible impact of the $\check A_6^0$ parameter on the ground state of CeRu$_4$Sn$_6$ leads to a reduction of the magnetic moment due to multiplet intermixing. The RIXS results are consistent with inelastic neutron scattering (INS) data and are compared to the predictions from \textsl{ab-initio} based electronic structure calculations.

Field evidence for the lateral emplacement of igneous dykes

Seismological and geodetic data from modern volcanic systems strongly suggest that magma is transported significant distance (tens of kilometres) in the subsurface away from central volcanic vents. Geological evidence for lateral emplacement preserved within exposed dykes includes aligned fabrics of vesicles and phenocrysts, striations on wall rocks and the anisotropy of magnetic susceptibility. In this paper, we present geometrical evidence for the lateral emplacement of segmented dykes restricted to a narrow depth range in the crust. Near-total exposure of three dykes on wave cut platforms around Birsay (Orkney, UK) are used to map out floor and roof contacts of neighbouring dyke segments in relay zones. The field evidence suggests emplacement from the WSW towards the ENE, and that the dykes are segmented over their entire vertical extent. Geometrical evidence for the lateral emplacement of segmented dykes is likely more robust than inferences drawn from flow-related fabrics, due to the prevalence of ubiquitous ‘drainback’ events (i.e. magmatic flow reversals) observed in modern systems.

Improved thermal conductivity of carbon-based thermal interface materials by high-magnetic-field alignment

Carbon-based fillers for thermal interface materials (TIMs) are attractive due to their advantages such as high thermal conductivity, low thermal expansion, mechanical strength, flexibility, and low weight. In this work, we report a 330% enhancement of the through-plane thermal conductivity (kth) of a graphite-polymer composite TIM film by vertically aligning the graphite fillers with a 10 T superconducting magnet. The filler alignment is based on the large anisotropy in the magnetic susceptibility of graphite platelets. As the filler content increases from 10 to 60 wt%, the anisotropy of thermal conductivity (kth/kin) increases from 1.2 up to 2.3 for a perpendicular magnetic field alignment, whereas it remains the same for a parallel magnetic field alignment. The increased anisotropy is associated with better filler alignment at high filler loadings. This work provides a simple and effective solution to improve the physical properties of composite films by controlling their microstructure.

Analytical solution of second-harmonic generation in a lithium-niobate-birefringence thin-film waveguide via modal phase matching

We present a systematic theoretical investigation of second-harmonic generation (SHG) in a subwavelength lithium niobate (LN) single-crystal thin-film waveguide with birefringence in permittivity and refractive index and strong anisotropy in the nonlinear susceptibility ${\ensuremath{\chi}}^{(2)}$. In a macroscopic birefringence LN crystal, the birefringence phase matching scheme that makes use of the refractive index management between the extraordinary light (EL) and ordinary light (OL) is dominantly used to ensure high-efficiency SHG. Yet, this scenario needs significant modification in a subwavelength LN thin film, where one should instead consider the waveguide modes of fundamental wave (FW) and second-harmonic wave (SHW) to participate in the SHG process. To this end, we first analytically solve and calculate the dispersion and modal profile of optical waveguide modes supported in the birefringence LN planar waveguide in a broad bandwidth ranging from ultraviolet to infrared regimes for TM (EL-like) and TE (OL-like) polarization states and at different waveguide thicknesses. Then we systematically examine the phase matching conditions that are necessary for high-efficiency energy conversion from FW waveguide mode to SHW waveguide mode via SHG. We find several modal phase matching schemes by exploiting the versatile freedoms of the FW and SHW waveguide mode number and polarization, and the waveguide thickness and symmetry. Yet modal phase matching only takes place at very limited discrete wavelengths of FW pump light. Under the modal phase matching condition, we derive the nonlinear coupled mode theory from Maxwell's equations and calculate the conversion efficiency of SHG, and find that the efficiency of SHG is determined by the nonlinear coupling coefficients that are closely associated with the modal profile overlap extent and mode transition strength between FW mode and SHW mode, and the involved nonlinear coefficient components of ${\ensuremath{\chi}}^{(2)}$. Finally, we have analytically derived the explicit formula that allows for direct calculation of the SHG efficiency as a function of the interaction length of FW mode and SHW mode, the nonlinear coupling coefficient, and the FW pump intensity, for both the small signal and general large signal situations. Our analytical theory and formulation can greatly facilitate the deep understanding of nonlinear optical interaction physics and provide a convenient tool for accurate quantitative evaluation of the SHG energy conversion efficiency of a pump laser in nanoscale LN single-crystal thin films. This analytical theory can also benefit for the design of nanoscale nonlinear optical devices based on the material platform of LN and other nonlinear crystal thin films.

Fault imprint in clay units: Magnetic fabric, p-wave velocity, structural and mineralogical signatures

We investigated the evolution of the structure, physical properties and fluid flow properties across a fault zone within the Toarcian shale formation from the Tournemire Underground Research Laboratory (France). With this purpose, an integrated approach was used based on the analysis of petrofabric (anisotropy of magnetic susceptibility, AMS, and of p-wave velocity, APV) and the mineralogy of two cores intercepting the F2 fault, a strike-slip fault with a small vertical offset.The fracture patterns indicated that the fault registered a multiphase tectonic evolution. Two strike-slip regimes, with approximate NE-SW and NW-SE compression, and a normal regime with a WNW-ESE direction of extension were identified. Most of the N-S fault planes collected in TF1 core, have a shallow dip with values between 5° to 45°.We further evidenced a close relationship between the fault architecture and petrophysical properties. A preferential NW-SE orientation of the K1 axes was observed that is in agreement with the extensional direction of the dextral movement of the fault. Within the fault core, an important decrease in anisotropy was observed and indicates clay platelets rotations related to tectonic deformation. A weaker anisotropic change was observed in ASM1. This difference may be related to the local variability of the fault zone and suggests the need to study the characteristics of a fault zone both across its different architectural zones and along the main fracture plan.Finally, we identified evidence of minerals alteration related to fault reactivation and fluid circulation. Fluid circulation enabled the transformation of siderite in magnetite, a neo-formation of kaolinite and a precipitation of calcite were at vicinity of the damage zone/fault core boundary.In TF1, while the major mineralogical changes occur in the damage zone. In ASM1, a higher illite-smectite mixed layers and calcite content was observed in the eastern side of the fault.

Characterizing seismites with anisotropy of magnetic susceptibility

This study was supported by grants from the Israeli Government under Geological Survey of Israel DS project 40706, and the Israel Science Foundation (ISF grants 868/17). We are indebted to Vladimir Lyakhovsky for helpful discussions during the course of this study, and to Mike Jackson, Bjarne Almqvist, and Jason Patton for providing constructive and very helpful reviews

A Study on Anisotropy of Magnetic Susceptibility of Clastic Sedimentary Rocks in the Gyeongsang Basin

A Study on Anisotropy of Magnetic Susceptibility of Clastic Sedimentary Rocks in the Gyeongsang Basin

Exploring circular polarization in the CMB due to conventional sources of cosmic birefringence

The circular polarization of the cosmic microwave background (CMB) is usually taken to be zero since it is not generated by Thomson scattering. Here we explore the actual level of circular polarization in the CMB generated by conventional cosmological sources of birefringence. We consider two classes of mechanisms for birefringence. One is alignment of the matter to produce an anisotropic susceptibility tensor: the hydrogen spins can be aligned either by density perturbations or CMB anisotropies themselves. The other is anisotropy of the radiation field coupled to the non-linear response of the medium to electromagnetic fields: this can occur either via photon-photon scattering (non-linear response of the vacuum); atomic hyperpolarizability (non-linear response of neutral atoms); or plasma delay (non-linear response of free electrons). The strongest effect comes from photon-photon scattering from recombination at a level of ∼ 10−14 K. Our results are consistent with a negligible circular polarization of the CMB in comparison with the linear polarization or the sensitivity of current and near-term experiments.

Multiple movements recorded in a crustal weakness zone in NE Iberia: The Vallès-Penedès Fault revisited

Structural analysis and Anisotropy of Magnetic Susceptibility are here applied to the fault zone (several hundreds of meters thick) associated with an E-W striking, 20 km-long segment of the Vallès-Penedès Fault (Catalan Coastal Ranges). The results obtained indicate a complex structure, mainly resulting from the imprint of Paleogene compressional events on a fabric inherited from the Variscan orogeny, and its Late-Variscan and Mesozoic extensional history. The prevailing foliation on the fault gouge and microbreccia is oblique (striking NW-SE) to the main E-W trace of the fault. S-C structures affecting the foliation show both sinistral and dextral shear components on NE-SW and NW-SE planes, respectively, consistent with horizontal striations on quartz rods and planar bodies. Pure reverse and normal dip-slip shear components are also inferred from S-C structures at the meso- and micro-scale, indicating a NW to N (reverse), and S-SSE (normal) transport directions. The magnetic foliation averages the orientation of the observed foliation at the outcrop scale and the magnetic lineation shows two maxima. The first maximum has an overall horizontal plunge, parallel to the strike-slip transport direction inferred from S-C structures. The second maximum is parallel to the dip direction of foliation planes and also parallelizes the reverse transport direction and occasionally the intersection lineation between S and C planes, thus revealing the strong heterogeneity and partitioning of deformation. Cataclasis and pressure-solution are the main deformation mechanisms, in agreement with clay composition and low paleotemperatures determined for the Paleogene. The presented results are consistent with Paleogene transpression occurred through strain partitioning between the main thrust separating the Catalan Coastal Range from the Ebro basin (reverse slip) and the Vallès-Penedès fault zone (sinistral strike-slip), with an important influence of dextral shear associated to the secondary, WNW-ESE, segment of the fault (either an oblique ramp or resulting from the re-activation of the Llobregat Fault). A subsequent, Neogene extensional imprint slightly modified the compressional fabrics in the fault zone.

The effects of variations in tissue microstructure from postmortem rat brain on the asymmetry of the water proton resonance.

This work was performed to investigate the effects of tissue microstructure from postmortem rat brain on the shape of the water proton spectrum. Perfusion-fixed, resected rat brains (N = 4) were imaged at 9.4T. 3D DTI and 3D echo-planar spectroscopic imaging (EPSI) data were acquired with 150 μm isotropic resolution. DTI data were acquired over 60 directions with b = 3000 s/mm2 . Water spectra were produced from EPSI data acquired over 128 echoes, with 2.9 Hz spectral resolution. A voxel-wise metric reflecting spectral asymmetry about the peak of the resonance was computed and compared with orientation estimates from DTI data by fitting data with the susceptibility anisotropy model. Asymmetric broadening of the water resonance was computed for mixed populations of grey and/or white matter as determined by thresholding the fractional anisotropy. Asymmetry was shown to be differentially affected by tract orientation relative to B0 in high FA voxels, whereas low FA voxels exhibited little sensitivity. Anatomic structures in the hippocampus were also found to produce distinct changes in the water resonance. Present results demonstrate that structural variations in tissue architecture cause characteristic, reproducible changes in the water resonance shape. This suggests that water spectra are sensitive to cytoarchitectural variations in brain tissue.

Investigating the Magmatic Plumbing System of a Monogenetic Scoria Cone: A Field and Laboratory Study of the Cienega Scoria Cone, Cerros del Rio Volcanic Field, New Mexico

AbstractData on the evolution of magmatic plumbing systems are essential for the understanding of magma motion in monogenetic volcanoes and associated volcanic hazard. Combined field (relationships and petrography) and laboratory (rock magnetism, anisotropy of magnetic susceptibility, and paleomagnetism) analysis of a quarried scoria cone offers a unique opportunity to study its magmatic plumbing system. In this study magma emplacement processes were constrained using these methods at two vents, Cerro Pequeño and Cerro Grande, of the composite Cienega scoria cone volcano, in New Mexico, USA. The dikes and lava flows associated with Cerro Pequeño were emplaced in two stages within a short period of time relative to secular variation. In the first stage, the magma was injected into the main conduit of the Cerro Pequeño and then channeled into secondary conduits (e.g., the exposed dike system) moving away from the vent. In the late stage, magma from the northern Cerro Grande was injected into the Cerro Pequeño dike system toward its main vent. The dynamic evolution of the magmatic system observed at the Cienega volcano is similar to that observed in other larger volcanic edifices. As in this study, the investigation of the magma plumbing systems of many scoria cones reveals that the subsurface magmatic system involves multiple feeder conduits that evolve during the life of the volcanic system. This study provides significant insight for the characterization of magma propagation at the shallow level beneath the volcanic edifice and highlights the related hazards associated with small active volcanic systems worldwide.

Petrophysical properties of volcanic rocks and impacts of hydrothermal alteration in the Guadeloupe Archipelago (West Indies)

The results of the GEOTREF project presented here aim to develop high enthalpy geothermal energy in fractured reservoirs. They focus on active volcanic islands, especially the Basse-Terre Island (Guadeloupe Archipelago). As part of this project we measured several petrophysical properties to better understand how fluids flow in the hydrothermal system, provide a set of parameters to modelers and build datasets for future interpretation of well logs. The thermo-physical rock properties of bulk and grain density, porosity, permeability, compressional wave velocity, thermal conductivity and diffusivity, specific heat capacity of outcropping volcanic rocks from the Guadeloupe Archipelago (Lesser Antilles) were measured and a dataset was built. According to field observations, samples were grouped into three lithological classes and then separated by their degree of alteration according to macroscopic aspects and optical microscopy results. Geochemical data were obtained, and magnetic minerals identified by combining anisotropy of magnetic susceptibility and variation of magnetic susceptibility with temperature.The lithotypes investigated were lava flows, debris flows and pyroclastics (gathering ash, pumice and scoria deposits). For lavas and debris flows, three degrees of alteration were defined; fresh, slightly to moderately altered and highly hydrothermalized. Only fresh pyroclastics were studied because the altered state was not outcropping.Typically, samples are composed of andesite and belong to tholeiitic and calc-alkaline series. Lava porosity consists of high-density cooling joints and vesicles of different shapes, whereas pores in debris flows and pyroclastics are located both between and within particles. Median porosities and permeabilities are clearly distinct for lavas (4% and 6 · 10−18 m2), debris flows (33% and 4 · 10−14 m2) and pyroclastics (34% and 8 · 10−13 m2). The porosity difference implies a thermal conductivity twice to three times higher for lavas (1.68 W·m−1·K−1). Specific heat capacity of all lithothypes is similar (0.75–0.97 kJ·kg−1·K−1).Advancing hydrothermal alteration removes magnetic minerals and transforms initial rocks. The original plagioclases and pyroxenes in neoformed chlorite, white micas, quartz, epidote and clay minerals are replaced. This modifies the shape of the pore network. Furthermore, hydrothermal alteration results in a reduction of pore throat diameter. It tends to decrease petrophysical differences between lavas and debris flows, increasing the porosity and permeability of effusive rocks, while the opposite effects are observed for debris flows.

Effects of grain size and texture on stress corrosion cracking of friction stir processed AZ80 magnesium alloy

Abstract The microstructure, mechanical properties, static and electrochemical corrosion, and stress corrosion cracking (SCC) behavior of friction stir processed AZ80 magnesium alloy were investigated, and the effects of grain size and texture on the SCC were analyzed. The results showed that fine-grained (FG) and coarse-grained (CG) specimens with the average grain size of 2.7 and 7.1 μm was obtained via friction stir processing (FSP) underwater and in air, respectively. Both specimens exhibited the similar characteristics of basal texture. The average microhardness of FG specimen (75.3 HV) was higher than that of CG specimen (69.4 HV) in the stir zone. Grain refinement enhanced both the corrosion and stress corrosion resistances in 3.5 wt% NaCl solution. The FG specimen exhibited obvious anisotropy in SCC susceptibility when tested along the processing and transverse directions during slow strain rate tensile test. Texture softening effect accelerated the formation of pitting corrosion, and decreased the SCC performance. Fracture surface of SCC exhibited transgranular brittle fracture. SCC behavior was controlled by anodic dissolution, and the hydrogen accelerated the SCC.

The carriers of AMS in remagnetized carbonates. Insights for remagnetization mechanism and basin evolution

Magnetic fabrics are usually studied to unravel the evolution of sedimentary basins, mainly focusing the attention in paramagnetic minerals. However, since basins are sometimes affected by burial-related chemical remagnetizations, magnetic fabrics can also be carried by authigenic ferromagnetic minerals related to remagnetization processes. Consequently, the study of the different types of fabrics can give complementary and valuable information about the evolution of sedimentary basins. Here, we explore, in the Jurassic carbonates of the Central High Atlas (Morocco), the role in magnetic fabrics of authigenic magnetite that grew during the Cretaceous (ca. 100 Ma) widespread remagnetization event.Magnetic fabrics are studied in 53 sites using the anisotropy of the magnetic susceptibility measured at room temperature (RT-AMS) and comparing results with sub-fabrics that alternatively enhance the paramagnetic and the ferromagnetic signal. Furthermore, an innovative analysis is proposed, comparing the magnetic fabrics before and after bedding correction (the common procedure) with fabric orientation after partial bedding correction. We use the paleomagnetic information to reconstruct the attitude of bedding at the remagnetization time and to restore the magnetic fabrics at this time.The performed analysis allows interpreting RT-AMS in terms of the contribution of different subfabrics, and the relationship between these, tectonic processes and the magnetic mineralogy. Four RT-AMS types are defined: T1 is carried by superparamagnetic magnetite that grew during the remagnetization stage and shows a horizontal lineation parallel to the extension direction at this time; T3 and T4 are carried by paramagnetic minerals and show compressive fabrics with the magnetic lineation parallel to intersection (bedding-cleavage) lineation; finally, T2 shows a mix between ferrimagnetic and paramagnetic fabrics.

Analysis of the magnetic properties of Ce3Pt23Si11: orthorhombic crystal field and mean-field approximation

We present here a quantitative analysis of the ground state and magnetic properties of Ce3Pt23Si11, based on a crystalline electric field description within the mean-field approximation. In this face-centered cubic compound, the point group symmetry at the Ce site is orthorhombic. One main difficulty in this low symmetry case is that the CEF potential for Ce3+ ions is determined by five independent parameters, while only two magnetic excitations are observed by inelastic neutron scattering. Moreover the anisotropy of the magnetic susceptibility of the Ce ion, that permits an independent determination of the second-order CEF parameters is hidden by the cubic symmetry of the compound. A specific procedure is developed for this purpose that combines genetic algorithms and more conventional optimization methods. A set of CEF parameters is found that best reproduces the different experimental observations in both the paramagnetic and ferromagnetic phases of Ce3Pt23Si11. The analysis accounts for two seemingly contradictory properties: a strong local anisotropy that aligns the moment along a fourfold axis and a rather weak anisotropy of the bulk magnetization with an easy threefold magnetization axis. Ce3Pt23Si11 is shown to be a model system where single site anisotropies compete within a crystal structure of overall high symmetry.

Diverse response of paramagnetic and ferromagnetic minerals to deformation from Intra-Carpathian Palaeogene sedimentary rocks: Comparison of magnetic susceptibility and magnetic remanence anisotropies

All the minerals in a rock contribute to its anisotropy of magnetic susceptibility (AMS). In weakly magnetic sedimentary rocks, the strongest contributors are the paramagnetic minerals, predominantly represented by clay minerals, together with the ferrimagnetic minerals that are typically magnetite and/or maghemite. In contrast, ferrimagnetic minerals solely control the anisotropy of magnetic remanence (AMR). An investigation of both AMS and AMR can therefore help distinguish among the deposition, diagenetic and deformation histories of the paramagnetic and ferrimagnetic minerals in the same rock specimen. We present a test case from relatively weakly deformed Intra-Carpathian Palaeogene sandstones (Skorušina Hills, Slovak Republic) where AMR and AMS fabrics generally coaxial yet also exhibited notable differences. In particular, AMR foliations were more readily deflected away from the bedding plane, perpendicular to the maximum stress axis, than the AMS foliations. These factors are interpreted in terms of higher sensitivity of the ferrimagnetic minerals to ductile deformation than that of the paramagnetic clay minerals.

NEOGENE TECTONIC ROTATIONS IN THE VICINITY OF THE NORTH AEGEAN TROUGH: NEW PALAEOMAGNETIC EVIDENCE FROM ATHOS AND SAMOTHRAKI (GREECE)

The present study focuses on two post-orogenic plutons, the Athos (Grigoriou) and Samothraki granites, as well as the Samothraki volcanics, located in the vicinity of the North Aegean Trough. A detailed palaeomagnetic study was carried out, with the aim of constraining the age and mechanism of tectonic rotations. In addition, anisotropy of low field magnetic susceptibility (AMS) was studied and isothermal remanent magnetization (IRM) and thermomagnetic analyses were performed. Finally, a radiometric age for the Athos granite was obtained (43.3 ± 1.0 Ma K/Ar biotite). The measured declinations indicate clockwise rotations of the Athos (16.6°) and Samothraki (36.3°) blocks. The age of rotation is constrained to be &lt;18 Ma at Samothraki, whereas the much smaller rotation of the Athos block can only be dated as younger than Eocene. Comparing the new palaeomagnetic data to the published dataset for Northern Greece, we suggest that the palaeomagnetically determined rotations in the vicinity of the North Aegean Trough are dominantly of post-Early Miocene age, and are controlled by major strike-slip faults and distributed "small" or minor faults.

Palaeocurrent and environmental implications from anisotropy of magnetic susceptibility (AMS): a case study from Talchir and Barakar formations, Raniganj Basin, West Bengal, India

Oriented cylindrical cores of rock samples were collected from the Talchir and Barakar formations of the Lower Gondwana Supergroup of the Raniganj Basin exposed in and around Kalyaneshwari and Maithon areas. The cores (2.54 cm diameter and 2.2 cm height) were studied in the low field anisotropy of magnetic susceptibility (AMS) measurement to determine the nature of magnetic fabrics, to correlate it with the sedimentological characteristics and to determine the palaeocurrent patterns. The results derived from the statistical parameters (especially the q-factor), the shapes of the susceptibility ellipsoids and directional data of the AMS indicate that the magnetic fabrics within the studied units are primary (depositional) and are correlatable form the palaeoenvironmental features. The orientation of the maximum (K1), intermediate (K2) and minimum (K3) susceptibility axes is dispersed on the lower hemisphere equal area diagram rather than strong clusters which is not because of secondary (tectonic) influence but due to the moderate to high-energy environment of deposition of the sediments in the studied units. Based on the q-factor (which is 0.581 for Barakar Formation and 0.565 for Talchir Formation which are both < 0.7), it is suggested the AMS indicates that the imbrication of the K1 axis is the indicator of palaeocurrent. Also, the magnetic foliation (average value = 1.255) exceeds the magnetic lineation (average value = 1.107) and the shape parameter exceeds 0 in most cases pointing towards an oblate fabric. The palaeocurrent in the present study as indicated by the K1 axis imbrication is very similar in both the units under study and is due SW. However, apart from this precise palaeocurrent direction, there exists a certain degree of randomness of the susceptibility axes which are very clear indication of corresponding depositional environments.