We investigated the properties of magnetic hysteresis loops of Iron Phthalocyanine (FePc) thin films using a Vibrating Sample Magnetometer (VSM). The FePc thin films were deposited onto heated silicon substrates. During deposition the FePc molecules self-assemble into small crystallites ranging in size from 30 to 300 nm on average. Due to the planar shape of the molecule, chains of iron atoms are formed. The magnetic interaction within a chain is much stronger than between chains, making these thin films quasi-one-dimensional magnetic systems. The average length of the major axis of the grains increases with the temperature of the substrate (deposition temperature). Essentially the thin films are made up of many randomly oriented iron chains of variable length, which are parallel to the substrate surface. We show that the coercivity of hysteresis loops measured at 2 K increases linearly with the average major axis grain length. From interpolation, the minimum average grain length for hysteresis to occur is 8 nm, and every additional nano-meter in length increases the coercivity by 72 Oe. By measuring hysteresis loops of many thin films of varying thickness we found that the saturation magnetization is 31 emu/cm3. This corresponds to 2.0 ± 0.6 µ B per iron ion, as compared to 2.22 µB for iron in a 3D lattice at 0 K. The choice of substrate also affects the hysteresis properties. Samples deposited on silicon substrates that had first been coated in gold with a rms roughness of approximately 1 nm will show much lower coercivity than corresponding silicon substrate samples. The planar gold surface allows for a different growth pattern in which the chains form vertically, perpendicular to the substrate. This lower coercivity suggests that the chains are shorter when vertically oriented.
|Commitee:||Bill, Andreas, Gu, Jiyeong|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 52/01M(E), Masters Abstracts International|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be