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Controlling exchange bias in Fe3O4/FeO composite particles prepared by pulsed laser irradiation.

Swiatkowska-Warkocka Z, Kawaguchi K, Wang H, Katou Y, Koshizaki N - Nanoscale Res Lett (2011)

Bottom Line: Through tuning the laser fluence, the Fe3O4/FeO phase ratio can be precisely controlled, and the magnetic properties of final products can also be regulated.This work presents a successful example of the fabrication of ferro (ferri) (FM)/antiferromagnetic (AFM) systems with high chemical stability.The results show this novel simple method as widely extendable to various FM/AFM nanocomposite systems.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, 305-8565 Ibaraki, Japan. zaneta.swiatkowska@aist.go.jp.

ABSTRACT
Spherical iron oxide nanocomposite particles composed of magnetite and wustite have been successfully synthesized using a novel method of pulsed laser irradiation in ethyl acetate. Both the size and the composition of nanocomposite particles are controlled by laser irradiation condition. Through tuning the laser fluence, the Fe3O4/FeO phase ratio can be precisely controlled, and the magnetic properties of final products can also be regulated. This work presents a successful example of the fabrication of ferro (ferri) (FM)/antiferromagnetic (AFM) systems with high chemical stability. The results show this novel simple method as widely extendable to various FM/AFM nanocomposite systems.

No MeSH data available.


Related in: MedlinePlus

Illustration of the FC and ZFC hysteresis loops. (a) Hysteresis loops of the Fe3O4/FeO particles fabricated at 177 mJ/pulse.cm2. FC means that the sample is cooled from 300 to 5 K in the 50 kOe field. (b) The magnification around origin of hysteresis loops of the Fe3O4/FeO particles fabricated at 177 mJ/pulse cm2.
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Figure 5: Illustration of the FC and ZFC hysteresis loops. (a) Hysteresis loops of the Fe3O4/FeO particles fabricated at 177 mJ/pulse.cm2. FC means that the sample is cooled from 300 to 5 K in the 50 kOe field. (b) The magnification around origin of hysteresis loops of the Fe3O4/FeO particles fabricated at 177 mJ/pulse cm2.

Mentions: Exchange coupling at the FM/AFM interface of the Fe3O4/FeO system is investigated by the zero field cooled (ZFC) and field cooled (FC) measurements of M(H). Figure 5 illustrates the FC (HFC = 50 kOe) and ZFC hysteresis loops at 5 K for a cycling field of ± 50 kOe of sample with 75% of wustite fraction (the ZFC and field cooled (FC) measurements of M(H) curves for particles with 20%, 45%, 60% and 85% of FeO are presented in supporting information on Figure S1 in Additional file 1). The interesting feature in the M(H) curves is that both the ZFC and FC loops remain open even in the 50 kOe field, known as the high field irreversibility, which could be interpreted as being due to the existence of the spin glass-like (SGL) phase [21,22]. According to the figure, this system exhibits the properties of exchange bias system, with a horizontal shift along the field axis of the FC hysteresis loop with respect to the ZFC hysteresis loop. The loop shift is defined as an exchange bias field Hexch = /(H+ + H-)/2/, where H+ and H- are positive and negative coercive fields. The FC hysteresis loop is shifted with an exchange bias field of 1,960 Oe. The coercivity field given by Hc = (H+ - H-)/2 is also obtained for both the ZFC case with the value of 514 Oe and a considerably higher value of 1950 Oe for FC cases. The large coercivity and exchange bias indicates a strong magnetic interaction through the interface between magnetite and wustite. Additionally, a slight positive vertical shift along the magnetization axis is presented. In FM/AFM systems, vertical shifts are generally related to pinned uncompensated spins that exhibit either FM or AFM coupling at the interface [23]. The positive vertical shift in Figure 5 indicates a dominant FM coupling between the pinned uncompensated spins and the FM magnetization.


Controlling exchange bias in Fe3O4/FeO composite particles prepared by pulsed laser irradiation.

Swiatkowska-Warkocka Z, Kawaguchi K, Wang H, Katou Y, Koshizaki N - Nanoscale Res Lett (2011)

Illustration of the FC and ZFC hysteresis loops. (a) Hysteresis loops of the Fe3O4/FeO particles fabricated at 177 mJ/pulse.cm2. FC means that the sample is cooled from 300 to 5 K in the 50 kOe field. (b) The magnification around origin of hysteresis loops of the Fe3O4/FeO particles fabricated at 177 mJ/pulse cm2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3211284&req=5

Figure 5: Illustration of the FC and ZFC hysteresis loops. (a) Hysteresis loops of the Fe3O4/FeO particles fabricated at 177 mJ/pulse.cm2. FC means that the sample is cooled from 300 to 5 K in the 50 kOe field. (b) The magnification around origin of hysteresis loops of the Fe3O4/FeO particles fabricated at 177 mJ/pulse cm2.
Mentions: Exchange coupling at the FM/AFM interface of the Fe3O4/FeO system is investigated by the zero field cooled (ZFC) and field cooled (FC) measurements of M(H). Figure 5 illustrates the FC (HFC = 50 kOe) and ZFC hysteresis loops at 5 K for a cycling field of ± 50 kOe of sample with 75% of wustite fraction (the ZFC and field cooled (FC) measurements of M(H) curves for particles with 20%, 45%, 60% and 85% of FeO are presented in supporting information on Figure S1 in Additional file 1). The interesting feature in the M(H) curves is that both the ZFC and FC loops remain open even in the 50 kOe field, known as the high field irreversibility, which could be interpreted as being due to the existence of the spin glass-like (SGL) phase [21,22]. According to the figure, this system exhibits the properties of exchange bias system, with a horizontal shift along the field axis of the FC hysteresis loop with respect to the ZFC hysteresis loop. The loop shift is defined as an exchange bias field Hexch = /(H+ + H-)/2/, where H+ and H- are positive and negative coercive fields. The FC hysteresis loop is shifted with an exchange bias field of 1,960 Oe. The coercivity field given by Hc = (H+ - H-)/2 is also obtained for both the ZFC case with the value of 514 Oe and a considerably higher value of 1950 Oe for FC cases. The large coercivity and exchange bias indicates a strong magnetic interaction through the interface between magnetite and wustite. Additionally, a slight positive vertical shift along the magnetization axis is presented. In FM/AFM systems, vertical shifts are generally related to pinned uncompensated spins that exhibit either FM or AFM coupling at the interface [23]. The positive vertical shift in Figure 5 indicates a dominant FM coupling between the pinned uncompensated spins and the FM magnetization.

Bottom Line: Through tuning the laser fluence, the Fe3O4/FeO phase ratio can be precisely controlled, and the magnetic properties of final products can also be regulated.This work presents a successful example of the fabrication of ferro (ferri) (FM)/antiferromagnetic (AFM) systems with high chemical stability.The results show this novel simple method as widely extendable to various FM/AFM nanocomposite systems.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, 305-8565 Ibaraki, Japan. zaneta.swiatkowska@aist.go.jp.

ABSTRACT
Spherical iron oxide nanocomposite particles composed of magnetite and wustite have been successfully synthesized using a novel method of pulsed laser irradiation in ethyl acetate. Both the size and the composition of nanocomposite particles are controlled by laser irradiation condition. Through tuning the laser fluence, the Fe3O4/FeO phase ratio can be precisely controlled, and the magnetic properties of final products can also be regulated. This work presents a successful example of the fabrication of ferro (ferri) (FM)/antiferromagnetic (AFM) systems with high chemical stability. The results show this novel simple method as widely extendable to various FM/AFM nanocomposite systems.

No MeSH data available.


Related in: MedlinePlus