antiferromagnetic materials where chromium is the only element exhibiting antiferromagnetism in the periodic table at room temperature.
3.5 Ferrimagnetism
Ferrimagnetism is observed in more complex crystal structures than pure elements.
The magnetic structure is composed of two magnetic sublattices separated by
oxygen. In a ferromagnetic material, some atoms are in parallel alignment while
others are in antiparallel alignment. The magnetic moments of the sublattices are not
equal and result in a net magnetic moment. The magnetic susceptibility is similar to
ferromagnetic materials, but ferrimagnetic materials usually have lower saturation
magnetizations. The material breaks down into magnetic domains where the diluting
effect of those atoms in antiparallel alignment keeps the magnetic strength of this
material generally less than that of purely ferromagnetic solids, a relatively low
magnitude as only one-eighth of the ions contribute to the magnetization of the
material [2]. A well-known ferrimagnetic material is a magnetite, Fe 3 O 4 .
4 Synthesis of Magnetic Particles
According to Thanh [18], the materials fabricated in the laboratory are mainly
composed of magnetite (Fe 3 O 4 ), maghemite (ɣ-Fe 2 O 3 ), greigite (Fe 3 S 4 ), and several
types of ferrites (MeOˑFe 2 O 3 , where Me ¼ Ni, Co, Mg, Zn, Mn, and others). Iron
oxide nanoparticles (Fe 3 O 4 and ɣ-Fe 2 O 3 ) have shown the most promise as potential
environmental magnetic sensing materials by way of the synthesis, tuning of physical properties, and surface functionalization [19].
Numerous methods of synthesizing magnetic particles such as coprecipitation,
hydrothermal, thermal decomposition, and sol-gel method have been so well
established. Some common methods to synthesize magnetic iron oxide nanoparticles
for versatility in tuning the characteristics of the nanomaterials are described in
Table 10.3. Furthermore, common inorganic coatings for magnetic nanoparticles are
presented in Table 10.4.
In order to be successfully exploited in applications, prerequisites such as good
dispersibility, nano-sized distribution, highly uniformed superparamagnetic properties, hydrophilic surface with different functional groups, as well as homogenous
physical and chemical properties are emphasized for the synthesis of iron oxide
nanoparticles [20]. The synthesis of the magnetic particles is divided into two
groups: in situ methods and ex situ methods.
400
S.-F. Lim et al.
3.5 Ferrimagnetism
Ferrimagnetism is observed in more complex crystal structures than pure elements.
The magnetic structure is composed of two magnetic sublattices separated by
oxygen. In a ferromagnetic material, some atoms are in parallel alignment while
others are in antiparallel alignment. The magnetic moments of the sublattices are not
equal and result in a net magnetic moment. The magnetic susceptibility is similar to
ferromagnetic materials, but ferrimagnetic materials usually have lower saturation
magnetizations. The material breaks down into magnetic domains where the diluting
effect of those atoms in antiparallel alignment keeps the magnetic strength of this
material generally less than that of purely ferromagnetic solids, a relatively low
magnitude as only one-eighth of the ions contribute to the magnetization of the
material [2]. A well-known ferrimagnetic material is a magnetite, Fe 3 O 4 .
4 Synthesis of Magnetic Particles
According to Thanh [18], the materials fabricated in the laboratory are mainly
composed of magnetite (Fe 3 O 4 ), maghemite (ɣ-Fe 2 O 3 ), greigite (Fe 3 S 4 ), and several
types of ferrites (MeOˑFe 2 O 3 , where Me ¼ Ni, Co, Mg, Zn, Mn, and others). Iron
oxide nanoparticles (Fe 3 O 4 and ɣ-Fe 2 O 3 ) have shown the most promise as potential
environmental magnetic sensing materials by way of the synthesis, tuning of physical properties, and surface functionalization [19].
Numerous methods of synthesizing magnetic particles such as coprecipitation,
hydrothermal, thermal decomposition, and sol-gel method have been so well
established. Some common methods to synthesize magnetic iron oxide nanoparticles
for versatility in tuning the characteristics of the nanomaterials are described in
Table 10.3. Furthermore, common inorganic coatings for magnetic nanoparticles are
presented in Table 10.4.
In order to be successfully exploited in applications, prerequisites such as good
dispersibility, nano-sized distribution, highly uniformed superparamagnetic properties, hydrophilic surface with different functional groups, as well as homogenous
physical and chemical properties are emphasized for the synthesis of iron oxide
nanoparticles [20]. The synthesis of the magnetic particles is divided into two
groups: in situ methods and ex situ methods.
400
S.-F. Lim et al.