Description: SUMMARY Palaeointensity estimates were made for a suite of five historical lava flows from Mt Askja, Iceland, with the purpose of testing the newly proposed domain-state corrections to the multispecimen parallel differential pTRM palaeointensity method (MSP), where pTRM stands for partial thermoremanent magnetization. Before beginning the experimental procedure, the chemical stability on heating to the determined pTRM induction temperature was assessed; some flows were found to be unaltered by heating, some displayed inconsistent repeatability, while one flow was severely affected by heating. To implement the domain-state corrections and interpret the data successfully, we had to implement two new approaches to the MSP method: (1) we used vector addition/subtraction in our calculations, and (2) we introduced a new selection/rejection criterion that improves the robustness of the estimates by preferentially removing outliers based on the error analyses of the linear regression. This rejection criterion typically rejected one or two points, and was found to significantly improve the estimates. With the exception of the one flow that displayed significant chemical alteration during the experiment, the palaeointensity estimates determined using the original MSP protocol yielded estimates within ±3 μT of the known field of 49.5 μT. The domain-state corrected MSP estimates were all within ±4 μT, with no clear relationship between the uncorrected and domain-state corrected palaeointensity estimates for this data set.

Description: SUMMARY Palaeomagnetic observations are being used in increasingly sophisticated geological and geophysical interpretations. It is therefore important to test the theories behind palaeomagnetic recording by rocks, and this can only be achieved using samples containing precisely controlled magnetic mineralogy, grain size and interparticle spacing, the last of which controls the degree of magnetostatic interactions within the samples. Here we report the room- and low temperature magnetic behaviour of a set of samples produced by the nano-scale patterning technique electron beam lithography. The samples consist of 2-D arrays of near-identical magnetite dots of various sizes, geometries and spatial configurations, with dot sizes from ranging from near the single domain threshold of 74–333 nm. We have made a series of magnetic measurements including hysteresis, first-order-reversal curve measurements and remanence acquisition, many as a function of temperature between 20 and 300 K, to quantify the samples’ behaviour to routine palaeomagnetic measurement procedures. We have also examined the behaviour of saturation isothermal remanences (SIRM) to cooling and warming cycling of the sample below room temperature. In addition, we investigated the samples’ responses to alternating-field demagnetization of room temperature induced SIRM, anhysteretic remanent magnetization (ARM) and partial ARM. ARM was used as a non-heating analogue for natural thermoremanence. Given the 2-D spatial distribution of the samples, in all the experiments we conducted both in-plane and out-of-plane measurements. Generally, the samples were found to display pseudo-single-domain hysteresis characteristics, but were found to be reliable recorders of weak-field remanences like ARM. For the closely packed samples, the samples’ magnetic response was highly dependent on measurement orientation.