Cov khoom sib nqus ntawm cov khoom siv yog ib chav kawm ntawm lub cev tshwm sim los ntawm cov teb. Cov hluav taws xob tam sim no thiab lub sij hawm sib nqus ntawm cov khoom siv hluav taws xob tsim hluav taws xob ua rau thaj chaw uas ua rau lwm cov dej ntws. Cov kev paub zoo tshaj plaws tshwm sim hauv cov ntaub ntawv ferromagnetic, uas tau nyiam los ntawm cov hlau nplaum thiab tuaj yeem ua cov hlau nplaum tas mus li, tsim cov chaw them nyiaj lawv tus kheej.
Tsuas yog ob peb yam tshuaj ferromagnetic. Txhawm rau txiav txim siab theem ntawm txoj kev loj hlob ntawm qhov tshwm sim hauv ib yam khoom, muaj kev faib cov khoom raws li cov khoom sib nqus. Feem ntau yog hlau, npib tsib xee thiab cob alt thiab lawv cov alloys. Lub npe ferro- yog hais txog hlau vim tias cov hlau nplaum ruaj khov tau pom thawj zaug hauv cov hlau tsis muaj hlau, ib daim ntawv ntawm cov hlau hlau hu ua cov khoom sib nqus ntawm cov khoom, Fe3O4.
Paramagnetic khoom
Txawm tiasferromagnetism yog lub luag haujlwm rau feem ntau ntawm cov teebmeem ntawm cov hlau nplaum uas tau ntsib nyob rau hauv lub neej txhua hnub, tag nrho lwm cov ntaub ntawv raug cuam tshuam los ntawm cov teb mus rau qee qhov, nrog rau qee yam ntawm cov hlau nplaum. Paramagnetic tshuaj xws li txhuas thiab oxygen tsis muaj zog txaus nyiam mus rau qhov chaw siv hlau nplaum. Cov tshuaj diamagnetic xws li tooj liab thiab cov pa roj carbon monoxide tsis muaj zog.
Thaum cov ntaub ntawv antiferromagnetic xws li chromium thiab spin iav muaj kev sib raug zoo nrog cov hlau nplaum. Lub zog ntawm cov hlau nplaum ntawm paramagnetic, diamagnetic, thiab antiferromagnetic cov ntaub ntawv feem ntau yog qhov tsis muaj zog thiab tsuas tuaj yeem kuaj pom los ntawm cov cuab yeej kuaj, yog li cov tshuaj no tsis suav nrog hauv cov npe ntawm cov khoom uas muaj cov khoom sib nqus.
Txoj Cai
Lub xeev sib nqus (los yog theem) ntawm cov khoom nyob ntawm qhov kub thiab txias thiab lwm yam hloov pauv xws li lub siab thiab siv cov hlau nplaum. Cov khoom siv tuaj yeem nthuav tawm ntau dua ib hom hlau nplaum raws li cov kev hloov pauv no.
History
Cov khoom sib nqus ntawm cov khoom siv tau pom thawj zaug hauv ntiaj teb thaum ub thaum tib neeg pom tias cov hlau nplaum, cov hlau nplaum ib txwm muaj peev xwm nyiam cov hlau. Lo lus "magnet" los ntawm Greek lo lus Μαγνῆτις λίθος magnētis lithos, "magnesian pob zeb, footstone".
Nyob rau hauv tim Nkij teb chaws thaum ub, Aristotle ntaus nqi thawj qhov uas yuav hu ua kev sib tham txog kev sib nqus ntawm cov khoom,philosopher Thales ntawm Miletus, uas nyob ntawm 625 BC. e. ua ntej 545 BC e. Cov ntawv kho mob Indian thaum ub Sushruta Samhita piav qhia txog kev siv cov hlau nplaum tshem tawm cov xub kos hauv tib neeg lub cev.
Ancient Tuam Tshoj
Hauv Suav teb thaum ub, cov ntawv sau ntxov tshaj plaws rau cov khoom siv hluav taws xob thiab sib nqus ntawm cov ntaub ntawv muaj nyob hauv phau ntawv 4-xyoo pua BC uas muaj npe tom qab nws tus kws sau ntawv, Sage of the Valley of Ghosts. Qhov ntxov tshaj plaws ntawm koob attraction yog nyob rau hauv lub xyoo pua 1st ua hauj lwm Lunheng (Sib npaug Thov): "Lub magnet attracts lub koob."
Lub xyoo pua 11th Suav tus kws tshawb fawb Suav Shen Kuo yog thawj tus neeg piav qhia - hauv Npau Suav Pas Dej Essay - lub ntsuas hluav taws xob sib nqus nrog rab koob thiab nws tau txhim kho qhov tseeb ntawm kev taug kev los ntawm txoj kev astronomical. lub tswv yim ntawm tseeb qaum teb. Los ntawm lub xyoo pua 12th, Suav tau paub tias siv cov hlau nplaum sib txuas rau kev taug kev. Lawv tau tsim cov diav rawg tawm ntawm pob zeb kom tus kov ntawm rab diav ib txwm taw rau sab qab teb.
Hnub Nyoog Kawg
Alexander Neckam, los ntawm 1187, yog thawj zaug hauv Tebchaws Europe los piav txog lub compass thiab nws siv rau kev taug kev. Tus kws tshawb fawb no thawj zaug hauv Tebchaws Europe tau tsim cov khoom ntawm cov khoom sib nqus. Nyob rau hauv 1269 Peter Peregrine de Maricourt tau sau Epistola de magnete, thawj txoj kev muaj sia nyob piav txog cov khoom ntawm cov hlau nplaum. Nyob rau hauv 1282, cov khoom ntawm compasses thiab cov ntaub ntawv nrog tshwj xeeb sib nqus zog tau piav qhia los ntawm al-Ashraf, ib tug Yemeni physicist, astronomer thiab geographer.
Renaissance
In 1600, William Gilbert luam tawmNws "Magnetic Corpus" thiab "Magnetic Tellurium" ("Ntawm Cov Hlau nplaum thiab Sib Nqus Lub Cev, thiab tseem nyob rau Lub Ntiaj Teb Magnet"). Hauv daim ntawv no, nws piav txog ntau yam ntawm nws qhov kev sim nrog nws lub ntiaj teb qauv, hu ua terrella, uas nws tau tshawb fawb txog cov khoom ntawm cov khoom sib nqus.
Los ntawm nws qhov kev sim, nws tuaj txog qhov xaus tias lub ntiaj teb nws tus kheej yog hlau nplaum thiab qhov no yog vim li cas cov compasses taw rau sab qaum teb (thaum ntxov, ib txhia ntseeg hais tias nws yog lub hnub qub ncej (Polaris) los yog ib kob hlau nplaum loj nyob rau sab qaum teb. Ncej uas nyiam lub compass).
sijhawm tshiab
Kev nkag siab ntawm kev sib raug zoo ntawm hluav taws xob thiab cov khoom siv nrog cov khoom sib nqus tshwj xeeb tau tshwm sim hauv xyoo 1819 hauv kev ua haujlwm ntawm Hans Christian Oersted, tus xibfwb ntawm University of Copenhagen, uas nrhiav pom los ntawm kev yuam kev twitching rab koob ze ze ntawm cov hlau uas muaj hluav taws xob. tam sim no tuaj yeem tsim ib qho chaw sib nqus. Qhov kev sim no yog lub npe hu ua Oersted Experiment. Ntau qhov kev sim ua raws li André-Marie Ampère, uas tau tshawb pom nyob rau xyoo 1820 tias thaj chaw sib nqus ncig nyob rau hauv txoj kev kaw tau cuam tshuam nrog cov tam sim no ntws ncig ib puag ncig ntawm txoj kev.
Carl Friedrich Gauss tau koom nrog kev kawm ntawm cov hlau nplaum. Jean-Baptiste Biot thiab Felix Savart hauv 1820 tau los nrog txoj cai Biot-Savart, uas muab qhov kev sib npaug xav tau. Michael Faraday, uas nrhiav tau nyob rau hauv 1831 hais tias lub sij hawm sib txawv sib nqus flux los ntawm ib lub voj ntawm hlau ua rau ib tug voltage. Thiab lwm cov kws tshawb fawb tau pom muaj kev sib txuas ntxiv ntawm cov hlau nplaum thiab hluav taws xob.
XX caug xyoo thiab pebtime
James Clerk Maxwell tau tsim thiab txuas ntxiv qhov kev nkag siab no ntawm Maxwell qhov sib npaug los ntawm kev sib koom ua ke hluav taws xob, hlau nplaum thiab optics hauv kev lag luam electromagnetism. Xyoo 1905, Einstein tau siv cov kev cai no los txhawb nws txoj kev xav ntawm kev sib raug zoo tshwj xeeb los ntawm kev xav kom cov kev cai lij choj muaj tseeb hauv txhua qhov kev siv inertial.
Electromagnetism tau txuas ntxiv mus rau hauv lub xyoo pua 21st, tau muab tso rau hauv ntau qhov kev xav ntawm kev ntsuas kev xav, quantum electrodynamics, electroweak txoj kev xav, thiab thaum kawg tus qauv qauv. Niaj hnub no, cov kws tshawb fawb twb tau kawm cov khoom sib nqus ntawm cov ntaub ntawv nanostructured nrog lub zog thiab lub ntsiab. Tab sis qhov kev tshawb pom zoo tshaj plaws thiab zoo tshaj plaws hauv daim teb no tej zaum tseem ua ntej ntawm peb.
Essence
Cov khoom sib nqus ntawm cov ntaub ntawv feem ntau yog vim lub sijhawm sib nqus ntawm lub orbital electrons ntawm lawv cov atoms. Lub sijhawm sib nqus ntawm atomic nuclei feem ntau yog ntau txhiab zaus me dua li cov khoom siv hluav taws xob, thiab yog li lawv tsis pom zoo hauv cov ntsiab lus ntawm cov khoom siv hlau nplaum. Nuclear magnetic moments tseem ceeb heev nyob rau hauv lwm yam ntsiab lus, tshwj xeeb tshaj yog nyob rau hauv nuclear magnetic resonance (NMR) thiab magnetic resonance imaging (MRI).
Feem ntau, cov khoom siv hluav taws xob loj loj tau teeb tsa hauv txoj hauv kev uas lawv lub sijhawm sib nqus (ob lub orbital thiab sab hauv) yog nullified. Rau qee qhov, qhov no yog vim qhov tseeb tias cov hluav taws xob sib xyaw ua ke nrog lub sijhawm sib nqus sib nqus sib nqus raws li lub hauv paus ntsiab lus ntawm Pauli (saib Electron configuration) thiab muab tso rau hauv cov subshells puv nrog xoom net orbital motion.
BNyob rau hauv ob qho tib si, cov electrons feem ntau siv circuits nyob rau hauv uas lub sij hawm sib nqus ntawm txhua lub electron raug tshem tawm los ntawm lub sij hawm opposite ntawm lwm electron. Tsis tas li ntawd, txawm tias thaum lub teeb tsa hluav taws xob zoo li muaj cov khoom siv hluav taws xob tsis sib xws thiab / lossis cov subshells tsis tiav, feem ntau yog qhov sib txawv ntawm cov khoom siv hluav taws xob sib txawv yuav ua rau lub sijhawm sib nqus sib nqus uas taw tes rau qhov sib txawv, random cov lus qhia, yog li cov khoom siv yuav tsis yog. Sib nqus.
Qee lub sij hawm, los ntawm tus kheej los yog vim yog siv sab nraud magnetic teb, txhua tus electrons 's magnetic moments yuav kab nyob rau nruab nrab. Cov khoom tsim nyog tuaj yeem tsim kom muaj zog net magnetic teb.
Tus cwj pwm sib nqus ntawm cov khoom yog nyob ntawm nws cov qauv, tshwj xeeb ntawm nws cov khoom siv hluav taws xob, rau cov laj thawj uas tau hais los saum no, thiab qhov kub thiab txias. Thaum qhov kub thiab txias, random thermal motion ua rau nws nyuaj rau electrons mus dlhos.
Diamagnetism
Diamagnetism muaj nyob rau hauv tag nrho cov ntaub ntawv thiab yog ib tug nyiam ntawm cov khoom los tiv thaiv ib tug siv magnetic teb thiab thiaj li repel lub magnetic teb. Txawm li cas los xij, nyob rau hauv cov khoom siv nrog cov khoom siv hluav taws xob (uas yog, nrog lub siab nyiam ntxiv dag zog rau sab nraud magnetic teb), tus cwj pwm paramagnetic dominates. Yog li, txawm tias qhov tshwm sim thoob ntiaj teb, tus cwj pwm diamagnetic tsuas yog pom nyob rau hauv cov khoom siv diamagnetic nkaus xwb. Tsis muaj cov khoom siv hluav taws xob tsis sib xws hauv cov khoom siv diamagnetic, yog li lub sijhawm sib nqus ntawm cov khoom siv hluav taws xob tsis tuaj yeem tsim.txhua yam teebmeem.
Thov nco ntsoov tias qhov kev piav qhia no yog tsim los ua kev xav xwb. Lub Bohr-Van Leeuwen theorem qhia tau hais tias diamagnetism yog tsis yooj yim sua raws li classical physics, thiab hais tias ib tug raug kev nkag siab yuav tsum tau ib tug quantum mechanical piav.
Nco ntsoov tias txhua yam ntaub ntawv dhau los ntawm cov lus teb no. Txawm li cas los xij, nyob rau hauv paramagnetic thiab ferromagnetic tshuaj, cov nyhuv diamagnetic yog suppressed los ntawm ntau zog los ntawm unpaired electrons.
Muaj cov khoom siv hluav taws xob tsis sib xws hauv cov khoom siv hluav taws xob; uas yog, atomic los yog molecular orbitals nrog raws nraim ib tug electron nyob rau hauv lawv. Thaum lub hauv paus ntsiab lus tsis suav nrog Pauli yuav tsum tau ua ke cov electrons kom muaj lawv tus kheej ("spin") lub sijhawm sib nqus taw tes rau hauv cov lus qhia sib txawv, ua rau lawv cov chaw sib nqus tshem tawm, ib qho hluav taws xob tsis sib xws tuaj yeem kho nws lub sijhawm sib nqus ntawm ob qho tib si. Thaum ib qho chaw sab nraud raug siv, cov sijhawm no yuav zoo li ua kom zoo ib yam li cov ntawv thov, ntxiv dag zog rau nws.
Ferromagnets
Ib qho ferromagnet, raws li cov khoom siv hluav taws xob, muaj cov hluav taws xob tsis sib xws. Txawm li cas los xij, ntxiv rau qhov nyiam ntawm lub sijhawm sib nqus ntawm cov khoom siv hluav taws xob mus rau qhov sib npaug ntawm cov ntawv thov, hauv cov ntaub ntawv no kuj tseem muaj kev nyiam rau cov sijhawm sib nqus no los taw qhia lawv tus kheej mus rau ib leeg txhawm rau txhawm rau tswj lub xeev ntawm kev txo qis. zog. Yog li, txawm tias tsis muaj daim ntawv thovlub sij hawm sib nqus ntawm cov electrons nyob rau hauv cov khoom spontaneously align parallel rau ib leeg.
Txhua yam tshuaj ferromagnetic muaj nws tus kheej qhov kub thiab txias, hu ua Curie kub, lossis Curie point, saum toj no uas nws poob nws cov khoom ferromagnetic. Qhov no yog vim hais tias lub thermal nyiam rau kev tsis sib haum xeeb overwhelms qhov txo ntawm lub zog vim ferromagnetic kev txiav txim.
Ferromagnetism tsuas yog tshwm sim hauv ob peb yam khoom; hlau, npib tsib xee, cob alt, lawv cov alloys, thiab qee qhov tsis tshua muaj lub ntiaj teb alloys.
Lub sijhawm sib nqus ntawm atoms hauv cov khoom siv ferromagnetic ua rau lawv coj zoo li cov hlau nplaum me me. Lawv lo ua ke thiab sib xyaw ua ke rau hauv thaj chaw me me ntawm ntau dua lossis tsawg dua kev sib koom ua ke hu ua magnetic domains lossis Weiss domains. Magnetic domains tuaj yeem pom tau siv lub tshuab magnetic force los qhia cov ciam teb sib nqus uas zoo li cov kab dawb hauv daim duab kos duab. Muaj ntau ntau yam kev sim uas tuaj yeem ua rau lub cev pom cov hlau nplaum.
Role of domains
Thaum ib lub npe muaj ntau cov molecules, nws yuav tsis ruaj khov thiab tawg mus rau hauv ob lub npe raws li cov lus qhia rov qab los ua ke ntau ruaj khov, raws li qhia ntawm sab xis.
Thaum raug rau thaj chaw sib nqus, cov ciam teb ntawm thaj chaw txav mus kom cov hlau nplaum sib xyaw ua ke loj hlob thiab tswj cov qauv (dotted yellow area), raws li qhia rau sab laug. Thaum lub teb magnetizing raug tshem tawm, cov thawj yuav tsis rov qab mus rau lub xeev uas tsis yog hlau nplaum. Qhov no ua rauvim tias cov khoom siv ferromagnetic yog hlau nplaum, tsim cov hlau nplaum ruaj khov.
Thaum lub magnetization muaj zog txaus kom lub dominant domain overlapped tag nrho cov lwm tus, ua rau tsim ntawm ib tug cais domain, cov khoom yog magnetically saturated. Thaum cov khoom siv hlau nplaum hlau nplaum yog rhuab mus rau qhov kub ntawm Curie point, cov molecules sib tov mus rau qhov chaw uas cov hlau nplaum sib nqus poob lub koom haum thiab cov khoom sib nqus lawv ua rau tsis muaj zog. Thaum cov khoom txias txias, qhov kev sib xyaw ua ke ntawm cov qauv no rov qab los, zoo ib yam li cov kua tuaj yeem khov rau hauv cov khoom siv crystalline.
Antiferromagnetics
Nyob rau hauv ib qho antiferromagnet, tsis zoo li ib tug ferromagnet, lub sij hawm sib nqus intrinsic ntawm cov nyob sib ze valence electrons nyiam taw tes rau hauv cov lus qhia. Thaum tag nrho cov atoms tau teem rau hauv ib yam khoom kom txhua tus neeg nyob ze yog antiparallel, cov khoom yog antiferromagnetic. Antiferromagnets muaj lub sijhawm sib nqus ntawm xoom, uas txhais tau tias lawv tsis tsim ib qho chaw.
Antiferromagnets tsis tshua muaj dua li lwm hom kev coj cwj pwm thiab feem ntau pom thaum qhov kub thiab txias. Ntawm qhov sib txawv ntawm qhov kub thiab txias, antiferromagnets nthuav tawm cov khoom diamagnetic thiab ferromagnetic.
Nyob rau hauv qee cov ntaub ntawv, cov electrons nyob sib ze nyiam taw tes rau cov lus qhia sib txawv, tab sis tsis muaj geometric kev npaj uas txhua khub ntawm cov neeg nyob sib ze tiv thaiv. Nws hu ua spin glass thiabyog ib qho piv txwv ntawm geometric ntxhov siab.
Cov khoom sib nqus ntawm cov khoom siv ferromagnetic
Zoo li ferromagnetism, ferrimagnets khaws lawv cov hlau nplaum thaum tsis muaj daim teb. Txawm li cas los xij, zoo li antiferromagnets, cov khub uas nyob ib sab ntawm electron spin zoo li taw tes rau cov lus qhia. Ob lub zog no tsis sib cav sib ceg vim tias, nyob rau hauv qhov kev pom zoo geometric, lub sijhawm sib nqus los ntawm lub sublattice ntawm electrons uas taw tes rau tib qho kev taw qhia yog ntau dua los ntawm sublattice uas taw tes rau qhov opposite direction.
Feem ntau ferrites yog ferrimagnetic. Cov khoom sib nqus ntawm cov ntaub ntawv ferromagnetic niaj hnub no suav tias yog qhov tsis lees paub. Thawj cov khoom sib nqus pom, magnetite, yog ferrite thiab tau xav tias yog ferromagnet. Txawm li cas los xij, Louis Neel tau lees paub qhov no los ntawm kev tshawb pom ferrimagnetism.
Thaum lub ferromagnet lossis ferrimagnet me me, nws ua raws li ib qho sib nqus sib nqus uas raug rau Brownian motion. Nws cov lus teb rau qhov chaw sib nqus yog qhov zoo ib yam li ntawm paramagnet, tab sis ntau ntxiv.
Electromagnets
Ib lub tshuab hluav taws xob yog cov hlau nplaum uas muaj cov hlau nplaum tsim los ntawm cov hluav taws xob tam sim no. Lub magnetic teb ploj thaum lub tam sim no muab tua. Electromagnets feem ntau muaj ntau qhov sib txuas sib txuas ntawm cov hlau uas tsim kom muaj qhov sib nqus. Hlau coils feem ntau raug mob nyob ib ncig ntawm ib tug hlau nplaum ua los ntawm ferromagnetic los yog ferrimagnetic khoom.ib yam khoom xws li hlau; cov tub ntxhais hlau nplaum concentrates cov hlau nplaum sib nqus thiab tsim cov hlau nplaum muaj zog.
Qhov txiaj ntsig tseem ceeb ntawm cov hlau nplaum hluav taws xob dhau ntawm cov hlau nplaum ruaj khov yog tias cov hlau nplaum tuaj yeem hloov pauv sai sai los ntawm kev tswj cov nqi hluav taws xob hauv qhov cua. Txawm li cas los xij, tsis zoo li cov hlau nplaum ruaj khov, uas tsis xav tau lub zog, lub tshuab hluav taws xob yuav tsum muaj cov khoom siv txuas ntxiv ntawm tam sim no kom tswj tau qhov sib nqus.
Electromagnets tau dav siv los ua cov khoom ntawm lwm yam khoom siv hluav taws xob xws li motors, generators, relays, solenoids, loudspeakers, hard drives, MRI machines, scientific instruments and magnetic separation equipment. Electromagnets kuj tau siv hauv kev lag luam los tuav thiab txav cov khoom hnyav hlau xws li cov hlau thiab hlau. Electromagnetism tau tshawb pom hauv xyoo 1820. Tib lub sijhawm, thawj qhov kev faib tawm ntawm cov ntaub ntawv raws li cov khoom sib nqus tau luam tawm.
