Single-domain Grains Research Articles

Are ceramics and bricks reliable absolute geomagnetic intensity carriers?

A detailed rock-magnetic and archeointensity study was carried out on materials baked by a western Mexican artisan following traditional techniques to produce faithful reproductions of archeological pieces of the Michoacán region (Western Mesoamerica). The field strength at the site (41.0 ± 0.5 μT) was measured with a fluxgate magnetometer and the temperature of the furnace during the baking process was monitored continually by means of a thermocouple placed in the middle of the baking cavity. Rock-magnetic experiments performed on the raw material (clay and paste) and on in situ prepared baked ceramics and bricks included measurement of thermomagnetic curves (susceptibility and strong-field magnetization versus temperature), first-order reversal curves (FORC), anisotropy of magnetic susceptibility (AMS) and anisotropy of thermoremanent magnetization (A-TRM). Magnetite and probably hematite are present in the samples as carriers of the remanence. Hysteresis ratios suggest that the samples fall in the pseudo-single-domain grain size region, which may indicate a mixture of multi-domain and a significant amount of single-domain grains. Ceramic pieces and brick fragments were subjected to the Thellier-Coe archeointensity method and to an alternative paleointensity experiment, with a TRIAXE magnetometer, in order to check whether they are faithful recorders of the local geomagnetic field strength. Mean raw-intensity of sample M1 (pottery) overestimates a 7% the expected site intensity, while those corresponding to the brick samples (LQ1 and LQ2) underestimate it 15%. Brick sample LNQ shows a slightly lower intensity (7%), but agrees with the expected site intensity within the experimental uncertainty. The intensity retrieved from the volcanic fragment also included closely reproduces the expected intensity. After A-TRM and cooling-rate corrections, all mean raw values move closer to the expected intensity. Measurement of temperatures at different parts inside the kiln (bottom and upper parts of both central and peripheral parts) revealed the existence of significant thermal gradients, similar to those observed in ovens from other localities. Different cooling rates are then expected in a single oven. The scatter in the intensity determinations observed in this study, retrieved from pieces elaborated together in the same oven, could arise from this differentiated cooling rate within the oven and thus, to an inappropriate cooling rate correction in the archeointensity protocol. As this situation was probably reproduced in the baking of ancient ceramic artifacts, a better knowledge of the temperature distribution inside these types of kiln would be desirable in order to choose the appropriate cooling rate correction.

Palaeointensity just at the onset of the Cretaceous normal superchron

A combined palaeomagnetic and geochronologic study has been conducted on a basaltic lava sequence of five flows at Jianchang in Liaoning Province, northeastern China. Radiometric 40Ar/ 39Ar dating indicates that the volcanism occurred at about 119 Ma within the marine anomaly C34n in Cretaceous normal superchron (CNS). Rock magnetic investigations show that pseudo-single domain (PSD) or a mixture of single domain and multi-domain grain titanium-poor titanomagnetite is dominant in the studied lava flows. Both stepwise thermal and alternating field demagnetizations isolate the well-defined normal characteristic remanent magnetization (ChRM) in five independent lava flows with a mean direction of D/ I = 11.1°/57.2° ( α 95 = 5.7°). Palaeointensity was determined using the Coe modified Thellier method with systematic partial thermoremanent magnetization (pTRM) checks. All together, 61 samples from 286 samples with positive pTRM and tail checks yield palaeointensities ranging between 10.1 and 73.6 μT. To further check the effects of thermal alteration on the palaeointensity results, a new ratio ( M rs,480°C/ M rs,25°C, where M rs,25°C and M rs,480°C are the room temperature saturation isothermal remanent magnetizations for the raw sample and the product after a 480 °C thermal treatment, respectively) is proposed. Results show that the ratio changes significantly even for those samples with positive pTRM check. We further put forward that palaeointensity results are acceptable with ratio between 0.9 and 1.1. With this new criteria, 17 samples show consistent palaeointensity results with an average of 20.0 ± 3.2 μT. This value corresponds to the virtual dipole magnetic moments (VDM) of (3.5 ± 0.6) × 10 22 Am 2, which is about half of the value of present field. This finding, combined with other available results, suggests that magnetic field of the Earth just at the onset of the CNS is characterized by a weak palaeointensity.

Physical basis of the Thellier–Thellier and related paleointensity methods

Émile and Odette Thellier produced the first reliable determinations of paleointensity following an experimental protocol used earlier by Johann Koenigsberger. Although Koenigsberger did groundbreaking work on thermoremanent magnetization (TRM), it was the Thelliers who formulated the fundamental idea of partial TRMs as building blocks for TRM. In his 1938 doctoral thesis and a series of short notes, Émile Thellier minutely examined the data on TRM and partial TRM, ultimately establishing for bricks and other baked clays his laws of pTRM reciprocity, independence and additivity. In 1946 he speculated that blocking represents “…immobilization of elementary magnetic moments below a temperature Θ … Θ will vary at each point in the body, perhaps with the dimensions and the shape of the crystalline grains … One can thus explain thermoremanence by the progressive fixing, in the course of cooling, of moments which find themselves held fast when they pass through their individual temperature Θ.” Thellier thus established the physical basis of TRM blocking and recognized the essential role of grain size and shape. In 1949 Louis Néel quantified these concepts in terms of the properties of single-domain grains. Today the Thellier–Thellier method remains the benchmark of reliable paleointensity data. The challenge has been the non-ideality of real geological and archeological materials: TRM carriers larger than single-domain size and physicochemical alteration during heating. The Thelliers avoided these problems by using bricks and pottery previously fired under conditions similar to those in laboratory heatings, eschewing volcanic and other rocks. But despite their problems, we have to deal with the material nature provides. This paper provides insights into the physics underlying the Thellier–Thellier method and check procedures that detect non-ideal behavior, as well as reviewing recent advances in paleointensity methodology.

A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 1. Theoretical framework

[1] The theoretical framework for a new nonheating method of determining absolute ancient magnetic field intensities (paleointensities) is described. The approach is based on a thermally activated Preisach model for interacting, randomly orientated single-domain grains with uniaxial anisotropy. The model includes theoretical features not accommodated by previous nonheating paleointensity methods; for example, it includes magnetostatic interactions, allows for variable cooling rates, and can identify, isolate, and reject unstable remanence carriers, i.e., multidomain and superparamagnetic contributions. The input Preisach distribution from which the acquisition of a thermal remanent magnetization (TRM) of a given rock sample can be simulated is obtained from information contained in the sample's first-order reversal curve distribution. The paleointensity estimate is determined by comparing the alternating field demagnetization spectrum of the sample's natural remanent magnetization and its simulated TRM. In the companion paper, the protocol is rigorously tested using a suite of historical samples.

Defect and impurity effects in exchange bias systems

We use a strong domain wall pinning model to interpret previous results on the effects of dopants and defects in the loop shift Hex of exchange bias systems. The effects of defects and dopants leads to a peak in the value of Hex as a function of the concentration, which was interpreted on the basis of the domain state model. We consider a strong domain wall pinning model such that the strength of the pins can lead to the formation of quasi-single domain grains. These single domain grains then behave as Stoner–Wohlfarth entities subject to thermal activation. This model provides excellent agreement with reported experimental data predicting the peak with concentration and the correct form of the variation in the peak shape with temperature.

Preparation and characterization of ZnSn-substituted barium ferrite thin films

The preparation of ZnSn-substituted barium ferrite films by sputtering deposition was studied. The as-sputtered films were amorphous, and annealing at a minimum of 750 °C was required to crystallize the films, based on the X-ray diffraction analysis and the magnetic measurements. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopic microanalysis confirmed that the films were single phase with the composition BaZn x Sn x Fe 12−2 x O 19, x=0.2−0.3, and their thicknesses were 0.4–1.0 μm when annealed at 750–900 °C. Atomic and magnetic force microscopy studies showed no significant grain growth upon annealing and that the films consisted of single-domain grains forming interaction-cluster-type domains. The natural ferromagnetic resonance frequency was determined at around 4 GHz, together with substantial magnetic losses that make these films promising candidates for microwave absorbers.

Analysis of magnetization and demagnetization processes in Nd-Fe-B sintered magnets using the step method

The magnetization and demagnetization processes in the 11 types of Dy-free Nd-Fe-B sintered magnets based on the NEOMAX-50 type magnets were investigated using the step method that is our original method of measurements and analyses of minor loops with step by step increased maximum applied fields. With the decrease in average grain sizes (DAVE), the single-domain grains (SDG) volume fraction increased and inversely that of the saturable multi-domain grains (SMDG) decreased, the changing behavior was monotonous. The dependence of coercivities on the DAVE, however, showed clear change around DAVE=3.0 μm, from the increase with decreasing DAVE to the opposite relationship less than DAVE ‹ 3.0 μm. We consider that the changing in the relationships should come from the ratios of the domain width (WD) to the DAVE, and conclude that the well cutting of magnetic interactions at the grain boundaries should realize the coercivity of μ0HC ≈ 2 T in fine grain size Dy-free samples.

Magnetic force microscopy investigation of the domain structure of nanocomposite Nd 2Fe 14B/Fe 3B magnets

In this paper, a detailed magnetic force microscopy study has been made of the domain structure of isotropic nanocomposite Nd 2Fe 14B/Fe 3B magnet ribbons prepared by melt-spinning. The domain structure is composed of interaction domains a few hundred nanometers in size, which indicates the presence of a strong exchange coupling between the grains. Within the interaction domains, a fine substructure on the same scale as the grain size is observed with high-contrast and clarity, which is an improvement over earlier results. As a consequence, the interaction domains are clusters of many single-domain grains whose magnetization directions are not precisely the same but differ slightly. In general, the interaction domains have both perpendicular and in-plane magnetization components. The domain width of the interaction domains (260 ± 20) nm was determined by digital means (using the method of Bodenberger and Hubert), in contrast to previous investigations.

Magnetic properties of rocks of the Kapuskasing uplift (Ontario, Canada) and origin of long-wavelength magnetic anomalies

SUMMARY The sources of long wavelength magnetic anomalies (LWA) in the crust are poorly understood. We have measured remanent and induced magnetizations of 210 samples of anorthosite, tonalite and mafic gneiss from the Kapuskasing uplift, an exposed partial crustal crosssection in northwestern Ontario, Canada. Anorthosites have generally high Q ratios of remanent/induced magnetization, in the range 0.3–60, and their natural remanent magnetization (NRM) is resistant to both thermal and alternating-field (AF) demagnetization. However, anorthositeNRMs(0.001–0.3Am −1 )aretooweaktoexplainLWAamplitudes.Maficgneisses also have relatively high Q ratios, peaking in the range 1–10, and the NRM is resistant to thermal and AF demagnetization. NRM and induced magnetization (IM) intensities are in the ranges 0.01–2 and 0.01–0.6 A m −1 , respectively. Tonalites have a bimodal distribution of magnetization. The more strongly magnetic group has both NRM and IM intensities in the range 0.1–5 A m −1 and wide-ranging Q values, from 0.1 to 10 approximately. Some tonalites could be an LWA source, although the long-term stability of their NRMs at high temperature in the crust is questionable because unblocking temperatures are broadly distributed from 100 to 600 ◦ C. In general, Q values measured at surface temperatures overestimate remanence at depth. In the deep crust, IM remains more or less constant but remanence decreases both reversibly and irreversibly, leading to Q ratios of <0.2–0.3 for multidomain grains and ≈1–3 for single-domain grains near their blocking temperatures. Thermoviscous magnetization over the Brunhes chron could add substantially to the effective induced magnetization. Typically induced + thermoviscous magnetization in the direction of the present Earth’s field will outweigh remanence in the direction of an ancient field as a source of LWA originating in the deepest crust. Remanence may play a larger role for mid-crustal sources where single-domain grains are well below their blocking temperatures.

Characterization and magnetic properties of Ba xSr 1− xFe 12O 19 ( x = 0–1) ferrite hollow fibers via gel-precursor transformation process

The Ba x Sr 1− x Fe 12O 19 ( x = 0–1) ferrite hollow fibers with diameters of 1 to 2 μm have been prepared by the gel-precursor transformation process. The gel-precursor decomposition and ferrite formation were analyzed by thermo-gravimetric and differential scanning calorimetry, infrared spectroscopy and X-ray diffraction. The Ba x Sr 1− x Fe 12O 19 ferrite hollow fibers as-prepared were characterized with scanning electron microscopy and vibrating sample magnetometer. The results show that the Ba x Sr 1− x Fe 12O 19 ( x = 0–1) ferrite hollow fibers are of a solid solution and these fibers with an obvious hollow structure consist of fine hexagonal plate-like particles. Their magnetic properties are mainly influenced by the chemical composition and grain size. With the barium substitution, the specific saturation magnetization and coercivity of the Ba x Sr 1− x Fe 12O 19 ferrite hollow fibers decrease from 67.1 Am 2/kg and 443.3 kA/m (for the simple SrFe 12O 19 ferrite, x = 0) to 56.1 A m 2/kg and 319.8 kA/m (for the simple BaFe 12O 19 ferrite, x = 1.0), respectively. The Ba 0.5Sr 0.5Fe 12O 19 ferrite hollow fibers calcined at 1000 °C for 2 h are composed of single-domain grains around 60 nm and exhibit the specific saturation magnetization 63.9 A m 2/kg and coercivity 416.5 kA/m.

Demagnetization of viscous moments

Summary. The theory of magnetism proposed by Walton is used-to produce models of magnetic viscous decay in an assembly of single domain grains of magnetite. These are then compared with data collected from carefully controlled viscosity experiments using 3 mm diameter cores of pottery whose major magnetic mineral is magnetite.

Effects of annealing time on the structural and magnetic properties of L1 0 FePt thin films

Thermal annealing of [Fe 1.65 nm/Pt 1.84 nm] 50 multilayers at 673 K for various annealing times between 60 and 12000 s leads to the direct formation of the fully ordered L1 0 FePt phase with (111) texture. The average grain sizes, determined from X-ray diffraction size–strain analysis, are smaller than the critical size for multi-domain FePt particles, suggesting the presence of single-domain (SD) grains. The coercivity increases with annealing time and increasing grain size and reaches values of about 955 kA/m. The remanence values are typical for randomly oriented weakly-interacting particles. A decrease of the remanence with annealing time suggests a decrease of the intergrain exchange interactions with annealing time. Analysis of minor loops and the initial magnetization curves shows the presence of a broad distribution of critical fields, which the individual SD particles have to overcome for the magnetization reversal.

Shock and static pressure demagnetization of pyrrhotite and implications for the Martian crust

The absence of crustal magnetization around young impact basins suggests impact demagnetization of vast regions of the crust after the cessation of the Martian dynamo. Attempts to understand the impact demagnetization process and to infer the magnetic properties (e.g., the carrier phase) of the Martian crust have been based on the experimental pressure demagnetization of magnetic rocks and minerals. We investigate the magnitude of demagnetization and permanent changes in the intrinsic magnetic properties of single and multidomain natural pyrrhotite under hydrostatic pressures up to 1.8 GPa and shock pressures up to 12 GPa. Both static and dynamic pressures result in an irreversible loss of predominantly low coercivity magnetic remanence. The pressure demagnetization results can be divided into a low-pressure regime and a high-pressure regime. The transition between the two regimes roughly coincides with a ferri- to paramagnetic transition (between 1.2 and 4.5 GPa) and the Hugoniot Elastic Limit (~ 3.5 GPa) of pyrrhotite. The low-pressure regime is characterized by a decrease in remanence with increasing pressure in both static and shock experiments. The higher pressure regime, probed only by shock experiments, is characterized by a more complicated modification of remanence as a result of permanent changes in the intrinsic magnetic properties of the material. These changes include an increase in saturation remanence and a change in the coercivity distribution towards greater bulk coercivity. Samples that were only submitted to hydrostatic pressure up to 1.8 GPa do not show permanent changes in the magnetic properties. Demagnetization of pyrrhotite as a result of pressure is likely due to a combination of domain reordering (in multidomain grains) and magnetostrictive effects (in single-domain grains). Microfracturing of multidomain grains effectively reduces the domain-size leading to the observed increase in single-domain like behavior. Based on uncertain shock pressure contours around basin-sized craters, impact demagnetization appears to be efficient at only a few GPa. Impact cratering affects the magnetic remanence of crustal rocks on all extraterrestrial bodies. For Mars, the pressure demagnetization results for pyrrhotite indicate that it is a possible carrier of the magnetization in the crust.

Magnetic force microscopy of combined reaction-processed polycrystalline equiatomic bulk L10 FePd

In this work, the correlation between magnetic-domain structure and microstructure in combined reaction-processed equiatomic L10 FePd has been investigated using magnetic force microscopy. The microstructure consisted of approximately equiaxed grains with an average grain size of ∼1 μm and a grain size distribution ranging from below the theoretical critical domain size (Dcrit∼0.2–0.3 μm) up to approximately 5 μm in diameter. The domain structure was characterized as “mixed” in nature, consisting of smaller single-domain grains, larger multidomain grains, and a larger scale interaction domain structure encompassing many grains. The domain boundaries separating interaction domains tended to lie along grain boundaries, and it is proposed that the observed interaction domains should be considered in descriptions of the magnetization and magnetization reversal behavior of this material. In particular, pinning of interaction domain walls by intragranular features of the microstructure such as grain boundaries and single-domain grains could play a role in the measured coercivities.

Optimal growth windows of multiferroic BiFeO 3 films and characteristics of ferroelectric domain structures

Multiferroic BiFeO 3 films of smooth surface and fully-saturated ferroelectric hysteresis loops have been grown by RF magnetron sputtering. The (001)-oriented epitaxial films showed a large remanent polarisation of 61 µC/cm 2. A strategy to grow BiFeO 3 films of good ferroelectric property was demonstrated, that was using fast growth rate to achieve accurate stoichiometry for the BiFeO 3 phase and at the same time to avoid the formation of impurity phases associated with the fast growth by accurate control of thermodynamic parameters such as oxygen partial pressure and temperature, as well as proper selection of substrates. Piezoresponse force microscopy revealed fine spontaneous domains for highly resistive epitaxial films, which were switchable under DC biases. For the polycrystalline films of increased density of free carriers, single-domain grains of about 200 nm in diameter were observed due to effective compensation of depolarisation field by free carriers and therefore allowing larger domains.

Formation of magnetite in Magnetospirillum gryphiswaldense studied with FORC diagrams

Abstract In order to study the formation of magnetite in magnetotactic bacteria, FORC diagrams were measured on a set of cultured Magnetospirillum gryphiswaldense, following an assay in which the iron uptake is used only for magnetite formation and not for cell growth. This enabled us to follow the magnetite formation independently of growth. The FORC diagrams showed a clear evolution from a size-distribution with a majority of superparamagnetic grains, to a distribution dominated by stable, single-domain grains, but still containing some superparamagnetic particles. TEM observations confirm this evolution. According to the saturation isothermal remanent magnetization cooling and warming curves, the Verwey transition can only be seen in the most mature samples, and slightly below 120 K. This suggests that the samples may have suffered from some partial oxidation.

Magnetic characteristics and archeointensity determination on Mesoamerican Pre-Columbian Pottery from Quiahuiztlan, Veracruz, Mexico

&#x0D; &#x0D; &#x0D; We report a detailed archeomagnetic investigation on pre-Columbian potteries from Quiahuiztlan, Veracruz, from ~900 AD to 1521 AD. Archeological samples analyzed by modern magnetic techniques carry a stable univectorial thermoremanent magnetization under alternating field treatment. Continuous low-field susceptibility vs. temperature curves performed in air indicates Ti-poor titanomagnetites as magnetization carriers. Few samples, however, show two ferrimagnetic phases with Curie temperatures compatible with both Ti-poor and Ti-rich titanomagnetites. Hysteresis parameter ratios fall essentially in the pseudo-single-domain region, which may indicate a mixture of multi-domain and a significant amount of single domain grains. Early geomagnetic field intensity determinations using the Coe variant of Thellier method were performed on 90 selected samples. Cooling rate corrected intensity values range from 34.0 ± 1.2 to 62.2 ± 0.2 ?T. Corresponding virtual axial dipole moments (VADM) range from 5.7 to 10.7 x1022 Am2. Absolute intensity curves for Mesoamerica present limited spa-tial/temporal resolution. For tentative dating purposes, we used global archeointensity curves reduced to central and eastern Mexico that permit preliminary dating of Quiahuiztlan potteries. Comparison of our data against those reported in ArcheoInt database allow to identify two periods 900- 1000 and 1400-1600 AD as the most probable manufacturing ranges for the pot- teries studied.&#x0D; &#x0D; &#x0D;

On the interpretation of normal and inverse magnetic fabric in dikes: Examples from the Eger Graben, NW Bohemian Massif

Recent studies of igneous rocks indicate that the predominant occurrence of normal/inverse fabric in dikes may either reflect the presence of multi-domain (MD)/single-domain (SD) grains or it may result from different orientation mechanisms of magnetic minerals in magmas of different viscosities. The ambiguity in physical vs. geological cause of normal/inverse magnetic fabric must be answered before any successful geological interpretation of magnetic fabric can be made. In order to address this problem, we studied magnetic fabric of selected dikes associated with the SW–NE trending Eger Graben (NW Bohemian Massif). The studied area offered very extensive collection of rock types: basanite, bostonite, camptonite, tinguaite, and trachybasalt. Magnetic susceptibility varies according to rock type and reflects the relative contents of magnetic minerals. In most cases, titanomagnetite with variable Ti content was identified as main magnetic carrier. The degree of anisotropy is relatively low, in most cases less than 10%, the shape of anisotropy ellipsoid ranges from slightly prolate to neutral and oblate. Several different types of magnetic fabric (using anisotropy of low-field magnetic susceptibility, AMS) were observed in studied dikes: so-called normal and inverse magnetic fabrics and anomalous magnetic fabric. Comparing all studied sites it seems that the type of magnetic fabric is lithology-dependent. Normal magnetic fabric with magnetic foliations and subhorizontal magnetic lineations both parallel to the dike margins was found in bostonite and trachybasalt dikes. Inverse magnetic fabric with magnetic lineations and magnetic foliations perpendicular to the dike margins was found in camptonite dikes. Anisotropy of anhysteretic remanent magnetization (AMR) indicate that the observed inverse magnetic fabric may be caused by the presence of SD magnetic grains; AMR fabric being normal with respect to dike margins. In contrast to that no single-domain particles were revealed using frequency dependence and anhysteretic susceptibility measurements. The AMS measured in variable weak magnetic fields is field dependent for camptonite dike and field independent for other rock types, i.e. bostonite, basanite, tinguaite, and trachybasalt. For further flow direction and tectonic interpretations of magnetic fabric in dikes it is suggested to use preferably the AMR fabric (at least for dikes which demonstrate significant field dependence of AMS) as it reflects the ‘true’ rock fabric more accurately than AMS fabric.

Dipolar interactions and their influence on the critical single domain grain size of Ni in layeredNi/Al2O3 composites

Pulsed laser deposition has been used to fabricateNi/Al2O3 multilayer composites in which Ni nanoparticles with diametersin the range of 3–60 nm are embedded as layers in an insulatingAl2O3 host. At fixed temperatures, the coercive fields plotted as a function of particle size showwell-defined peaks, which define a critical size that delineates a crossover fromcoherently rotating single domain to multiple domain behavior. We observe a shift inpeak position to higher grain size as temperature increases and describe this shiftwith theory that takes into account the decreasing influence of dipolar magneticinteractions from thermally induced random orientations of neighboring grains.

Induced Magnetization of Magnetite-titanomagnetite in Alternating Fields Ranging from 400 A/m to 80,000 A/m; Low-field Susceptibility (100 – 400 A/m) and Beyond

For remanence-bearing minerals (RBM) such as magnetite-titanomagnetite, susceptibility to induced magnetism (M) measured in alternating fields (HAC) is field-dependent. However, for fields ≤ 400 A/m, measured in an AC induction coil instrument (at 19,100 Hz), susceptibility k0 = M/HAC is sufficiently linear to provide a reproducible rock (or mineral) magnetic characteristic and its anisotropy may be related to arrangements of minerals in rock, or for single mineral grains to their crystalline or shape anisotropy. For any remanence-bearing mineral at higher fields kHF (= M/HAC) is not constant and the term susceptibility is not normally used. This study bridges the responses between traditional low-field susceptibility measurements and those due to high applied fields, for example when studying hysteresis or saturation magnetization of RBM. Where |kHF| is measured in alternating fields that peak significantly above 400 A/m the M(HAC) relation is forced to follow a hysteresis loop in which |kHF| > k0 for small |HAC| and where |kHF| decreases to zero for very large fields that achieve saturation magnetization. Hysteresis nonlinearity is due to remanence acquired with one field direction requiring a reverse field for its cancellation. We investigate the transition from initial, traditional “low-field” susceptibility (k0) measurements at 60 A/m, through 24 different fields from 400 A/m to 40,000 A/m (for very high k0 to 80,000 A/m). This reveals M(HAC) dependence beyond from conventional k0 through the range of hysteresis behavior in fields equal to and exceeding that required to achieve saturation magnetization (MS). We show kHF increases with peak HAC until the peak field is slightly less than saturation magnetization in natural rock samples rich in magnetite (TM0 = Fe3O4) and TM60 (Fe2.4Ti0.6O4). All sample suites predominantly contain multidomain grains with subordinate pseudo-single domain and single-domain grains. k/k0 increases by ≤ 5% for fields up to 2 kA/m. Above 4 kA/m k/ k0 increases steeply and peaks, usually between 24 kA/m and 30 kA/m where all grains magnetic moments are activated by HAC since this exceeds the coercive force of most grains. For higher peak HAC, k/k0 declines sharply as increased HAC values more effectively flip M with each field-direction switch, leading to the low gradient at distal portions of the hysteresis loop. For M0-TM60 bearing rocks, susceptibility peaks for fields ~12 kA/m and for magnetite rich rocks up to 24 kA/m. These values are approximately 10% of saturation magnetizations (MS) reported for the pure minerals from hysteresis DC field measurements. Both the field at peak k/k0 and the peak k/k0 value appear to be controlled by the dominant domain structure; multidomain behavior has larger k/k0 peaks at lower HAC. Stacked k/k0 versus HAC curves for each sample suite (n = 12 to n = 39) were successfully characterized at the 95% level by a polynomial fit that requires the cubic form k/k0 = a + bH + cH2 + dH3. Thus, for most M-TM bearing rocks, susceptibility and anisotropy of susceptibility (AMS) measurements made on different instruments would be sufficiently precise for most geological applications, if peak alternating fields are ≤700 A/m.