BAHAN MAGNETIK
Klasifikasi bahan magnetik Berdasarkan responnya terhadap medan magnetik, bahan magnetik dikelompokkan dalam tiga kelompok utama 1. Diamagnetik 2. Paramagnetik 3. Ferro-, ferri-, antiferromagnetik
Diamagnetik (1)
Suseptibilitas magnetik kecil dan negatif M H
Diamagnetik (2)
Suseptibilitas magnetik tidak bergantung pada temperatur
Contoh mineral diamagnetik Mineral
κ (SI)
Quartz (SiO2)
- (13-17) x 10-6
Calcite (CaCO3)
- (8-39) x 10-6
Graphite (C)
- (80-200) x 10-6
Halite (NaCl)
- (10-16) x 10-6
Sphalerite (ZnS)
- (0.77-19) x 10-6 Data from Hunt et al (1995)
Paramagnetik (1) Suseptibilitas magnetik kecil dan positif H = 0, M = 0
H > 0, M > 0
H
Paramagnetik (2) Suseptibilitas magnetik bergantung pada temperatur
Hukum Curie-Weiss
Contoh mineral paramagnetik Mineral
κ (SI)
Olivine (Fe,Mg)2SiO4
1.6 · 10-3
Montmorillonite (clay)
0.34 ·10-3
Siderite (FeCO3)
1.3-11.0 · 10-3
Serpentinite (Mg3Si2O5(OH)4)
3.1-75.0 · 10-3
Chromite (FeCr2O4)
3-120 · 10-3 Data from Hunt et al (1995)
Mineral ferromagnetik : FeO-TiO2-Fe2O3 Diagram Ternary
Ferromagnetik (1) Suseptibilitas magnetik bernilai positif dan besar Magnetic ordering H=0
M≠ 0 Unsur ferromagnetik : • Iron (Fe)
• Cobalt (Co)
• Nickel (Ni)
• Gadolinium (Gd)
Antiferromagnetik dan non-perfect antiferromagnetik Antiferromagnetik
Non- perpect antiferromagnetik (spin-canted antiferromagnetik)
M= 0
Unsur antiferromagnetik : • Chromium (Cr) • Manganese (Mn)
M Contoh: Hematite (Fe2O3)
Ferrimagnetik
M
Contoh: Magnetite (Fe3O4)
Kurva histeresis M = Ms
M= Msr
M=0
Summary Diamagnetism Paramagnetism
Ferromagnetism
Non-perfect Antiferromagnetism Antiferromagnetism
Ferrimagnetism
important for rock and paleomagnetism
Bahan magnetik berdasarkan ukuran SPM (superparamagnetik) SD (single domain) PSD (pseudo-single domain) MD (multidomain)
Magnetic domain (1)
Domain adalah daerah pada bahan magnetik yang mempunyai spinning electron bebas.
single domain
dua domain
empat domain
closure domain
Magnetic domain (2) Tanda panah menunjukkan dipol magnetik. Dalam masing-masing domain, semua dipol sejajar, sedangkan arah dipol antara satu domain dengan yang lainnya bervariasi.
Domain wall Domain wall merupakan daerah transisi antar domain di mana magnetisasi mempunyai arah yang berbeda.
Iron single crystal photomicrographs Domain magnetik berubah bentuk ketika bahan magnetik dikenakan pada medan magnetik
c18f13
Konfigurasi domain pada beberapa tahap magnetisasi
Magnetite Chemical Fe++Fe+++2O4 Formula: Composition: Molecular Weight = 231.54 gm Iron 72.36 % Fe 31.03 % FeO / 68 .97 % Fe2O3 Oxygen 27.64 % O Empirical Fe3+2Fe2+O4 Formula: Environment: Common accessory mineral in igneous and metamorphic rocks. Can be biogenically produced by a wide variety of organisms. Locality: Many localities and environments world wide. Name Origin: Named for Magnes, a Geek shepherd, who discovered the mineral on Mt, Ida, He noted that the nails of his shoe and the iron ferrule of his staff clung to a rock.
Sifat Fisis Magnetite Cleavage: Color: Density: Habit: Habit: Habit: Hardness: Luminescence: Luster: Magnetism: Streak:
None Grayish black, Iron black. 5.1 - 5.2, Average = 5.15 Crystalline - Fine - Occurs as well-formed fine sized crystals. Massive - Granular - Common texture observed in granite and other igneous rock. Massive - Uniformly indistinguishable crystals forming large masses. 5.5-6 - Knife Blade-Orthoclase Non-fluorescent. Metallic Naturally strong black
Hematite Chemical Fe2O3 Formula: Composition: Molecular Weight = 159.69 gm Iron 69.94 % Fe 100.00 % Fe2O3 Oxygen 30.06 % O Empirical Fe3+2O3 Formula: Environment: Magmatic, hydrothermal, metamorphic and sedimentary. Locality: Matto Grosso, Brazil. Mesabi iron ore range, Minnesota, USA. Link to MinDat.org Location Data. Name Origin: From the Greek, haimatites, "bloodlike'" in allusion to vivid red color of the powder.
Sifat Fisis Hematite Cleavage: Color: Density: Fracture: Habit: Habit: Habit: Hardness: Luminescence: Luster: Magnetism: Streak:
None Reddish gray, Black, Blackish red. 5.3 Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz). Blocky - Crystal shape tends to be equant (e.g. feldspars). Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite). Tabular - Form dimensions are thin in one direction. 6.5 - Pyrite Non-fluorescent. Metallic Magnetic after heating reddish brown
Maghemite Chemical gamma-Fe+++2O3 Formula: Composition: Molecular Weight = 159.69 gm Iron 69.94 % Fe 100.00 % Fe2O3 Oxygen 30.06 % O Empirical Fe3+2O3 Formula: Environment: Formed by weathering or lowtemperature oxidation of spinels containing ferrous iron, commonly magnetite or titanian magnetite. Widespread yellow pigment in sediments. Name From MAGnetite and HEMatite, in allusion Origin: to the mineral's magnetism and composition.
Sifat Fisis Maghemite Cleavage: Color: Density: Fracture:
Habit: Habit: Hardness: Luster: Magnetism: Streak:
None Dark brown. 4.9 Sub Conchoidal - Fractures developed in brittle materials characterized by semi-curving surfaces. Massive - Granular - Common texture observed in granite and other igneous rock. Massive - Uniformly indistinguishable crystals forming large masses. 6 - Orthoclase Metallic Strongly magnetic brown
Goethite Chemical Fe+++O(OH) Formula: Composition: Molecular Weight = 88.85 gm Iron 62.85 % Fe 89.86 % Fe2O3 Hydrogen 1.13 % H 10.14 % H2O Oxygen 36.01 % O Empirical Fe3+O(OH) Formula: Environment: Common in iron ore deposits. Name Origin: Named after the German poet, J. W. Goethe (1749-1832)
Sifat Fisis Goethite Cleavage: Color: Density: Fracture: Habit: Habit: Habit: Hardness: Luminescence: Luster: Streak:
{010} Perfect, {100} Distinct Brown, Reddish brown, Yellowish brown, Brownish yellow, Ocher yellow. 3.3 - 4.3, Average = 3.8 Hackly - Jagged, torn surfaces, (e.g. fractured metals). Acicular - Occurs as needle-like crystals. Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite) Reniform - "Kidney like" in shape (e.g.. hematite). 5-5.5 - Apatite-Knife Blade Non-fluorescent. Adamantine - Silky yellowish brown
Citra SEM – mineral magnetik (1)
Huliselan et al., 2010
Citra SEM – mineral magnetik (2)
R-9998
MO-4228
Citra SEM – mineral magnetik (3)
KS
M Brown
KP
Citra SEM – mineral magnetik (4)
Fly ash
Magiera et al., 2011
