[S-EM18] [EE] General Contributions in Geomagnetism, Paleomagnetism, and Rockmagnetism

[SEM18-P13] Composition law of oblique anhysteretic remanent magnetization and its relation to the magnetostatic interaction

*佐藤 雅彦¹、望月 伸竜²、渡邉 美奈子³、綱川 秀夫⁴ (1.産業技術総合研究所、2.熊本大学、3.長岡工業高等専門学校、4.東京工業大学)

キーワード：Anhysteretic Remanent Magnetization, Magnetostatic Interaction, Rock Magnetism

The basic properties of oblique anhysteretic remanent magnetization (OARM) acquired in a weak and steady magnetic field with an arbitrary angle to the alternating field direction were studied. OARM and rock-magnetic experiments were conducted on samples of basalt, granite, and sediment containing non-interacting single-domain (SD), interacting SD, pseudo-single-domain, and multidomain low-Ti titanomagnetites. The intensity of OARM (M_OARM) systematically increased or decreased with increasing angle between alternating and steady field directions (θ_SF), while the angle between alternating field and OARM directions (θ_OARM) increased with increasing θ_SF for all samples. During stepwise alternating field demagnetization, the OARM vector shows a single component parallel to the steady field direction for θ_SF = 0° (ARM_||) and 90° (ARM_⊥). The median destructive field of ARM_⊥ is larger than that of ARM_||. For intermediate angles (θ_SF = 30°, 45°, and 60°), the OARM vector was not parallel to the applied steady field; instead, it gradually increased with coercivity. These experiments indicate that the OARM vector is approximately given by the sum of two orthogonal magnetizations coinciding with ARM_|| and ARM_⊥, respectively. Thus, the OARM vector can be determined by acquisition efficiencies of ARM_|| and ARM_⊥ in an individual sample. Based on these experiments and associated rock-magnetic measurements, non-interacting SD samples show lower ARM_⊥/ARM_|| ratios, compared to other samples. This result suggests that OARM can be used as a conventional tool to detect non-interacting SD particles in the paleomagnetic samples.