TY - JOUR
T1 - Behavior of u-channels during acquisition and demagnetization of remanence
T2 - Implications for paleomagnetic and rock magnetic measurements
AU - Brachfeld, Stefanie A.
AU - Kissel, Catherine
AU - Laj, Carlo
AU - Mazaud, Alain
PY - 2004/7/30
Y1 - 2004/7/30
N2 - We have examined the effects of translation speed on the acquisition and demagnetization of remanence in u-channels. The speed at which the u-channel moves through alternating and steady fields has a significant effect on the efficiency of remanence acquisition and demagnetization. Anhysteretic remanence (ARM) acquisition and alternating field (AF) demagnetization efficiency are inversely correlated with translation speed. ARM acquisition is most efficient at a track speed of 1 cm/s, whereas at higher speeds ARM reaches an apparent saturation at low peak fields and has a soft coercivity spectrum during subsequent AF demagnetization. The dependence of magnetization (acquired or removed) on translation speed through alternating or steady fields is explained by the number of alternating field half-cycles experienced as the sample is translated through the applied field and on the alternating field decay rate. At slow translation speeds a u-channel experiences a comparable number of alternating field cycles to that experienced by a stationary discrete sample. At fast translation speeds, the u-channel experiences a factor of 100 fewer alternating field cycles, and the conditions experienced by the u-channel sample can be comparable to the natural reorganization time of the magnetic moments within the sediment particles during remanence acquisition and demagnetization. At low decay rates the sample has more time in the blocking field and thus a more complete approach to equilibrium.
AB - We have examined the effects of translation speed on the acquisition and demagnetization of remanence in u-channels. The speed at which the u-channel moves through alternating and steady fields has a significant effect on the efficiency of remanence acquisition and demagnetization. Anhysteretic remanence (ARM) acquisition and alternating field (AF) demagnetization efficiency are inversely correlated with translation speed. ARM acquisition is most efficient at a track speed of 1 cm/s, whereas at higher speeds ARM reaches an apparent saturation at low peak fields and has a soft coercivity spectrum during subsequent AF demagnetization. The dependence of magnetization (acquired or removed) on translation speed through alternating or steady fields is explained by the number of alternating field half-cycles experienced as the sample is translated through the applied field and on the alternating field decay rate. At slow translation speeds a u-channel experiences a comparable number of alternating field cycles to that experienced by a stationary discrete sample. At fast translation speeds, the u-channel experiences a factor of 100 fewer alternating field cycles, and the conditions experienced by the u-channel sample can be comparable to the natural reorganization time of the magnetic moments within the sediment particles during remanence acquisition and demagnetization. At low decay rates the sample has more time in the blocking field and thus a more complete approach to equilibrium.
KW - Alternating field demagnetization
KW - Anhysteretic remanent magnetization
KW - Paleomagnetism
KW - Relative paleointensity
KW - Rock magnetism
KW - U-Channel
UR - http://www.scopus.com/inward/record.url?scp=2942729433&partnerID=8YFLogxK
U2 - 10.1016/j.pepi.2003.12.011
DO - 10.1016/j.pepi.2003.12.011
M3 - Article
AN - SCOPUS:2942729433
SN - 0031-9201
VL - 145
SP - 1
EP - 8
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
IS - 1-4
ER -