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Hoʻomalu ʻia nā waiwai magnetic o SrFe12O19 (SFO) hexaferrite paʻakikī e ka pilina paʻakikī o kāna microstructure, kahi e hoʻoholo ai i ko lākou pili ʻana i nā noi magnet mau loa.E koho i kahi pūʻulu o nā nanoparticles SFO i loaʻa ma ka sol-gel combustion synthesis, a hana i ka hohonu o ka X-ray powder diffraction (XRPD) characterization e G(L) line profile analysis.ʻO ka hāʻawi ʻana i ka nui crystallite e hōʻike ana i ka hilinaʻi maopopo ʻana o ka nui ma ke ala [001] ma ke ʻano hana synthesis, e alakaʻi ana i ka hoʻokumu ʻana i nā crystallites flaky.Eia kekahi, ua hoʻoholo ʻia ka nui o nā nanoparticles SFO e ka hoʻoili ʻana i ka microscopy electron (TEM), a ua manaʻo ʻia ka helu awelika o nā crystallites i nā ʻāpana.Ua loiloi ʻia kēia mau hopena e hōʻike i ka hoʻokumu ʻana o nā mokuʻāina hoʻokahi ma lalo o ka waiwai koʻikoʻi, a loaʻa ka leo hoʻāla mai nā ana magnetization pili i ka manawa, e kuhikuhi ana i ka wehewehe ʻana i ke kaʻina hana magnetization o nā mea magnetic paʻakikī.
He koʻikoʻi koʻikoʻi ka ʻepekema a me ka ʻenehana nui nā mea magnetic nano-scale, no ka mea, hōʻike ko lākou mau waiwai magnetic i nā ʻano like ʻole i hoʻohālikelike ʻia me ko lākou nui leo, e lawe mai i nā hiʻohiʻona hou a me nā noi1,2,3,4.Ma waena o nā mea nanostructured, M-type hexaferrite SrFe12O19 (SFO) ua lilo i moho uʻi no nā noi magnet mau loa5.ʻO kaʻoiaʻiʻo, i nā makahiki i hala iho nei, ua hana ʻia ka nui o nā hana noiʻi ma ka hoʻopilikino ʻana i nā mea e pili ana i ka SFO ma ka nanoscale ma o nā ʻano synthesis a me nā ʻano hana e hoʻonui ai i ka nui, morphology, a me nā waiwai magnetic6,7,8.Eia kekahi, ua loaʻa ka manaʻo nui i ka noiʻi a me ka hoʻomohala ʻana i nā ʻōnaehana hoʻohui hoʻololi9,10.ʻO kāna anisotropy magnetocrystalline kiʻekiʻe (K = 0.35 MJ / m3) e pili ana i ka c-axis o kāna lattice hexagonal 11,12 he hopena pololei ia o ka pilina paʻakikī ma waena o ka magnetism a me ka hoʻolālā aniani, nā crystallites a me ka nui o ka palaoa, morphology a me ke ʻano.No laila, ʻo ka hoʻomalu ʻana i nā ʻano ma luna ke kumu no ka hoʻokō ʻana i nā koi kikoʻī.Hōʻike ka Kiʻi 1 i ka pūʻulu ākea hexagonal maʻamau P63/mmc o SFO13, a me ka mokulele e pili ana i ka noʻonoʻo ʻana o ka noiʻi hōʻike hōʻike laina.
Ma waena o nā hiʻohiʻona e pili ana i ka emi ʻana o ka nui o ka ferromagnetic particle, ʻo ka hoʻokumu ʻana i kahi mokuʻāina hoʻokahi ma lalo o ka waiwai koʻikoʻi e alakaʻi i ka hoʻonui ʻana i ka anisotropy magnetic (ma muli o kahi kiʻekiʻe o ka ʻili i ka ratio volume), kahi e alakaʻi ai i kahi kahua coercive14,15.ʻO ka ʻāpana ākea ma lalo o ka nui koʻikoʻi (DC) i nā mea paʻakikī (ʻo ka waiwai maʻamau ma kahi o 1 µm), a ua wehewehe ʻia e ka mea i kapa ʻia ʻo coherent size (DCOH)16: pili kēia i ke ala liʻiliʻi loa no ka demagnetization i ka nui coherent. (DCOH), Hōʻikeʻia e like me ka leo hoʻoulu (VACT) 14. Eia naʻe, e like me ka mea i hōʻikeʻia ma ka Figure 2,ʻoiaiʻoi aku ka liʻiliʻi o ka kristal ma mua o DC, hikiʻole ke hoʻololi i ke kaʻina hana hoʻohuli.Ma nā ʻāpana nanoparticle (NP), ʻo ka nui koʻikoʻi o ka hoʻohuli ʻana e pili ana i ka viscosity magnetic (S), a ʻo ka hilinaʻi ʻana i ka māla magnetic e hāʻawi i ka ʻike nui e pili ana i ke kaʻina hana hoʻololi o NP magnetization17,18.
Maluna: Hoʻolālā kiʻi o ka hoʻololi ʻana o ke kahua koʻikoʻi me ka nui o nā ʻāpana, e hōʻike ana i ke kaʻina hana hoʻohuli magnetization (hoʻololi ʻia mai ka 15).Ke kū nei ʻo SPS, SD, a me MD no ka mokuʻāina superparamagnetic, hoʻokahi domain, a me multidomain, kēlā me kēia;Hoʻohana ʻia ʻo DCOH a me DC no ke anawaena coherence a me ke anawaena koʻikoʻi.Malalo: Nā kiʻi o nā ʻāpana like ʻole, e hōʻike ana i ka ulu ʻana o nā crystallites mai ka aniani hoʻokahi a i ka polycrystalline.ahōʻike i ka nui o ka crystallite a me ka nui o nā ʻāpana.
Eia nō naʻe, ma ka nanoscale, ua hoʻokomo ʻia nā ʻano paʻakikī hou, e like me ka pilina magnetic ikaika ma waena o nā ʻāpana, ka hāʻawi ʻana i ka nui, ke ʻano o ka particle, ka maʻi ʻili, a me ke kuhikuhi o ka axis maʻalahi o ka magnetization, ʻo ia mau mea a pau e ʻoi aku ka paʻakikī. 20 .Hoʻopilikia nui kēia mau mea i ka hāʻawi ʻana i ka ikehu a pono e noʻonoʻo pono, a laila e pili ana i ke ʻano hoʻohuli magnetization.Ma kēia kumu, he mea nui e hoʻomaopopo pono i ka pilina ma waena o ka leo magnetic a me ke kino nanostructured M-type hexaferrite SrFe12O19.No laila, ma ke ʻano he ʻōnaehana kumu hoʻohālike, ua hoʻohana mākou i kahi pūʻulu o nā SFO i hoʻomākaukau ʻia e kahi ʻano sol-gel i lalo, a ua hana hou i ka noiʻi.Hōʻike nā hualoaʻa mua i ka nui o nā crystallites i ka nanometer range, a ʻo ia, me ke ʻano o nā crystallites, pili i ka mālama wela i hoʻohana ʻia.Eia kekahi, pili ka crystallinity o ia mau laʻana i ke ʻano synthesis, a koi ʻia ka ʻike kikoʻī e wehewehe i ka pilina ma waena o nā crystallites a me ka nui o nā ʻāpana.I mea e hōʻike ai i kēia pilina, ma o ka hoʻoili ʻana i ka microscopy electron (TEM) i hui pū ʻia me ke ʻano Rietveld a me ka nānā ʻana i ka laina laina o ka helu kiʻekiʻe X-ray pauda diffraction, ua nānā pono ʻia nā ʻāpana microstructure kristal (ʻo ia hoʻi, nā crystallites a me ka nui o ka particle, shape) .XRPD).ʻO ka manaʻo o ka Structural characterization ka manaʻo e hoʻoholo i nā ʻano anisotropic o nā nanocrystallites i loaʻa a e hōʻoia i ka hiki ke hoʻopaʻa ʻia o ka ʻikepili laina ma ke ʻano he ʻenehana ikaika no ka ʻike ʻana i ka hoʻonui ʻana i ka piko i ka laulā nanoscale o nā mea (ferrite).Ua ʻike ʻia ʻo ka hāʻawi ʻana i ka nui crystallite i hoʻopaʻa ʻia i ka leo G(L) e hilinaʻi nui ʻia i ka kuhikuhi crystallographic.Ma kēia hana, hōʻike mākou he pono maoli nā ʻenehana hou e unuhi pololei i nā ʻāpana pili i ka nui e wehewehe pono i ke ʻano a me nā hiʻohiʻona magnetic o ia mau laʻana pauda.Ua aʻo pū ʻia ke kaʻina hana o ka hoʻohuli ʻana i ka magnetization no ka wehewehe ʻana i ka pilina ma waena o nā hiʻohiʻona morphological structure a me ka hana magnetic.
Hōʻike ʻia ka ʻikepili Rietveld o ka X-ray powder diffraction (XRPD) i ka nui o ka crystallite ma ka axis c hiki ke hoʻololi ʻia e ka mālama wela kūpono.Hōʻike pololei ia i ka hoʻonui ʻia ʻana o ka piko i ʻike ʻia i kā mākou laʻana ma muli paha o ke ʻano kristal anisotropic.Eia kekahi, ʻo ke kūlike ma waena o ke anawaena awelika i kālailai ʻia e Rietveld a me ka diagram Williamson-Hall (ama ka Papa S1) e hōʻike ana i nā crystallites ua aneane ʻaʻohe kānana a ʻaʻohe deformation hoʻolālā.ʻO ka ulu ʻana o ka hāʻawi ʻana i ka nui crystallite ma nā ʻaoʻao like ʻole e kālele ana i ko mākou manaʻo i ka nui o nā mea i loaʻa.ʻAʻole maʻalahi ka nānā ʻana, no ka mea, ʻo ka hāpana i loaʻa ma ka sol-gel combustion spontaneous i haku ʻia me nā agglomerates o nā ʻāpana me kahi hoʻolālā porous6,9, iwakāluakūmākahi.Hoʻohana ʻia ʻo TEM e aʻo i ke ʻano o loko o ka laʻana hoʻāʻo i nā kikoʻī hou aku.Hōʻike ʻia nā kiʻi brightfield maʻamau ma ke Kiʻi 3a-c (no ka wehewehe kikoʻī o ka nānā ʻana, e ʻoluʻolu e nānā i ka pauku 2 o nā mea hoʻohui).Aia ka hāpana i nā ʻāpana me ke ʻano o nā ʻāpana liʻiliʻi.Hoʻohui pū nā platelets e hana i nā hui porous o nā ʻano nui a me nā ʻano like ʻole.I mea e manaʻo ai i ka nui o ka hāʻawi ʻana i nā platelets, ua ana lima ʻia ka ʻāpana o nā ʻāpana 100 o kēlā me kēia laʻana me ka hoʻohana ʻana i ka polokalamu ImageJ.ʻO ke anawaena o ka pōʻai like me ka ʻāpana ʻāpana like me ka waiwai e pili ana i ka nui o kēlā me kēia ʻāpana i ana ʻia.Ua hōʻuluʻulu ʻia nā hopena o nā laʻana SFOA, SFOB a me SFOC ma ke Kiʻi 3d-f, a ua hōʻike pū ʻia ka waiwai anawaena awelika.ʻO ka hoʻonuiʻana i ka mahana hana e hoʻonui i ka nui o nā'āpana a me ko lākou ākea ākea.Mai ka hoʻohālikelike ʻana ma waena o VTEM a me VXRD (Papa 1), hiki ke ʻike ʻia ma ke ʻano o SFOA a me SFOB samples, ʻo ka helu awelika o nā crystallites ma kēlā me kēia ʻāpana e hōʻike ana i ke ʻano polycrystalline o kēia mau lamellae.I ka hoʻohālikelike ʻana, ua hoʻohālikelike ʻia ka nui o ka SFOC me ka nui o ka crystallite awelika, e hōʻike ana i ka hapa nui o nā lamellae he mau kristal hoʻokahi.Hōʻike mākou he ʻokoʻa ka nui o ka TEM a me X-ray diffraction, no ka mea, ma ka hope, ke ana nei mākou i ka poloka hoʻopuehu pili (ʻoi aku ka liʻiliʻi ma mua o ka flake maʻamau): Eia kekahi, ke kuhi hewa liʻiliʻi o kēia mau lūlū. E helu ʻia nā kāʻei kapu e ka ʻokoʻa.
Hōʻike nā kiʻi TEM kahua ʻālohilohi o (a) SFOA, (b) SFOB a me (c) SFOC ua haku ʻia lākou me nā ʻāpana me ke ʻano like me ka pā.Hōʻike ʻia nā māhele nui e pili ana i ka histogram o ka panel (df).
E like me kā mākou i ʻike ai i ka nānā mua ʻana, ʻo nā crystallites i loko o ka hāpana pauda maoli e hana i kahi ʻōnaehana polydisperse.Ma muli o ka maʻalahi loa o ke ʻano X-ray i ka poloka hoʻopuehu coherent, pono ka nānā pono ʻana i ka ʻikepili diffraction pauda e wehewehe i nā nanostructure maikaʻi.Maʻaneʻi, kūkākūkāʻia ka nui o nā crystallites ma o keʻano o ka hana hāʻawi nui crystallite nui-nui G (L) 23, hiki ke unuhiʻia ma keʻano o ka nui o ka loaʻaʻana o nā crystallites i manaʻoʻia i keʻano a me ka nui, a ua like kona kaumaha me ka ia.Volume, i ka hāpana i kālailai ʻia.Me ke ʻano crystallite prismatic, hiki ke helu ʻia ka nui o ka crystallite i hoʻopaʻa ʻia i ka volume (ka lōʻihi ʻaoʻao ma nā kuhikuhi [100], [110] a me [001]).No laila, ua koho mākou i ʻekolu mau laʻana SFO me nā ʻāpana like ʻole i ke ʻano o nā flakes anisotropic (e nānā i ka Reference 6) e loiloi i ka pono o kēia kaʻina hana e loaʻa ai ka hāʻawi ʻana i ka nui crystallite pololei o nā mea nano-scale.No ka loiloi i ka anisotropic orientation o nā crystallites ferrite, ua hana ʻia ka nānā ʻana o ka laina laina ma ka ʻikepili XRPD o nā piko i koho ʻia.ʻAʻole i loaʻa i nā laʻana SFO i hoʻāʻo ʻia ka ʻokoʻa (maʻemaʻe) kiʻekiʻe o ka hoʻonohonoho ʻana o nā mokulele aniani, no laila ʻaʻole hiki ke hoʻokaʻawale i ka hāʻawi hoʻonui laina mai ka nui a me ka distortion.Ma ka manawa like, ʻoi aku ka nui o ka hoʻonui ʻia ʻana o nā laina diffraction ma muli o ka hopena nui, a ua hōʻoia ʻia ke ʻano crystallite awelika ma o ka nānā ʻana o kekahi mau laina.Hoʻohālikelike ka Kiʻi 4 i ka hana hāʻawi nui crystallite-kaumaha G(L) ma ka ʻaoʻao crystallographic i wehewehe ʻia.ʻO ke ʻano maʻamau o ka hāʻawi ʻana i ka nui crystallite he lognormal distribution.ʻO kekahi hiʻohiʻona o nā puʻunaue nui i loaʻa ʻia ko lākou unimodality.I ka hapanui o nā hihia, hiki ke hoʻopili ʻia kēia māhele i kekahi kaʻina hana i wehewehe ʻia.ʻO ka ʻokoʻa ma waena o ka awelika i helu ʻia o ka piko i koho ʻia a me ka waiwai i unuhi ʻia mai ka hoʻomaʻemaʻe ʻo Rietveld i loko o kahi ākea kūpono (e noʻonoʻo ana he ʻokoʻa nā kaʻina hana calibration ma waena o kēia mau ʻano) a ua like ia me ka hoʻonohonoho ʻana o nā mokulele e. Debye Ua kūlike ka nui awelika i loaʻa me ka Scherrer equation, e like me ka mea i hōʻike ʻia ma ka Papa 2. ʻO ke ʻano o ka nui o ka nui crystallite awelika o nā ʻenehana hoʻohālike like ʻole he ʻano like loa, a he liʻiliʻi loa ka deviation o ka nui piha.ʻOiai paha he mau kuʻikahi me Rietveld, no ka laʻana, ma ke ʻano o ka (110) noʻonoʻo o SFOB, pili paha ia i ka hoʻoholo pololei ʻana o ke kua ma nā ʻaoʻao ʻelua o ka noʻonoʻo i koho ʻia ma kahi mamao o 1 degere 2θ i kēlā me kēia. kuhikuhi.Eia naʻe, ʻo ka ʻaelike maikaʻi loa ma waena o nā ʻenehana ʻelua e hōʻoia i ka pili o ke ʻano.Mai ka nānā ʻana o ka hoʻonui ʻana i ka piko, ʻike ʻia ka nui o ka [001] i hilinaʻi kikoʻī i ke ʻano synthesis, e hopena i ka hoʻokumu ʻana o nā crystallites flaky i SFO6,21 i hoʻohui ʻia e ka sol-gel.Ke wehe nei kēia hiʻohiʻona i ke ala no ka hoʻohana ʻana i kēia ʻano hana e hoʻolālā i nā nanocrystals me nā ʻano makemake.E like me kā mākou e ʻike ai, ʻo ke ʻano kristal paʻakikī o SFO (e like me ka mea i hōʻike ʻia ma ke Kiʻi 1) ʻo ia ke kumu o ka ʻano ferromagnetic o SFO12, no laila hiki ke hoʻoponopono ʻia ke ʻano a me ka nui o nā hiʻohiʻona e hoʻolālā i ka hoʻolālā o ka laʻana no nā noi (e like me ka paʻa mau. pili magnet).Hōʻike mākou he ala ikaika ka nānā ʻana i ka nui crystallite e wehewehe i ka anisotropy o nā ʻano crystallite, a hoʻoikaika hou i nā hopena i loaʻa mua.
(a) SFOA, (b) SFOB, (c) SFOC noʻonoʻo i koho ʻia (100), (110), (004) puunaue ka nui crystallite paona G(L).
I mea e loiloi ai i ka pono o ke kaʻina hana no ka loaʻa ʻana o ka hāʻawi ʻana i ka nui crystallite kikoʻī o nā mea nano-powder a hoʻopili iā ia i nā nanostructures paʻakikī, e like me ka hōʻike ʻana ma ka Figure 5, ua hōʻoia mākou i kēia ʻano hana i nā mea nanocomposite (nominal waiwai).ʻO ka pololei o ka hihia i haku ʻia me SrFe12O19/CoFe2O4 40/60 w/w %).Ua kūlike loa kēia mau hopena me ka Rietveld analysis (e ʻike i ka caption o ka Figure 5 no ka hoʻohālikelike ʻana), a ke hoʻohālikelike ʻia me ka ʻōnaehana hoʻokahi, hiki i nā nanocrystals SFO ke hōʻike i kahi morphology e like me ka pā.Manaʻo ʻia kēia mau hopena e hoʻopili i kēia hōʻike ʻikepili laina i nā ʻōnaehana paʻakikī kahi e hiki ai ke uhi ʻia nā ʻano aniani like ʻole me ka nalowale ʻole o ka ʻike e pili ana i kā lākou mau hale.
ʻO ka hāʻawi ʻia ʻana o ka nui crystallite nui G (L) i koho ʻia o SFO ((100), (004)) a me CFO (111) i nā nanocomposites;no ka hoʻohālikelike ʻana, ʻo 70 (7), 45 (6) a me 67 (5) nm6 nā waiwai loiloi Rietveld e pili ana.
E like me ka mea i hōʻike ʻia ma ke Kiʻi 2, ʻo ka hoʻoholo ʻana i ka nui o ka domain magnetic a me ka helu kūpono o ka leo kino ke kumu no ka wehewehe ʻana i ia ʻōnaehana paʻakikī a no ka hoʻomaopopo pono ʻana i ka pilina a me ka hoʻonohonoho ʻana ma waena o nā ʻāpana magnetic.I kēia mau lā, ua aʻo nui ʻia ka ʻano hoʻohālikelike o nā laʻana SFO, me ka nānā pono ʻana i ke kaʻina hoʻohuli o ka magnetization, i mea e aʻo ai i ka mea hiki ʻole ke hoʻololi ʻia o ka hiki ke hoʻololi ʻia (χirr) (Figure S3 he laʻana o SFOC)6.I mea e loaʻa ai ka ʻike hohonu o ka mīkini hoʻohuli magnetization i kēia nanosystem ferrite-based, ua hana mākou i kahi ana hoʻomaha hoʻomaha magnetic ma ke kahua hope (HREV) ma hope o ka saturation ma kahi kuhikuhi.E noʻonoʻo i ka \(M\left(t\right)\proptoSln\left(t\right)\) (e nānā i ke Kiʻi 6 a me nā mea hoʻohui no nā kikoʻī hou aku) a laila e loaʻa ka leo hoʻāla (VACT).No ka mea hiki ke wehewehe ʻia ʻo ia ka leo liʻiliʻi loa o nā mea i hiki ke hoʻohuli like ʻia i loko o kahi hanana, hōʻike kēia ʻāpana i ka leo "magnetic" i loko o ke kaʻina hana hoʻohuli.ʻO kā mākou waiwai VACT (e nānā i ka Papa S3) pili i kahi pōʻai me ke anawaena o kahi kokoke i 30 nm, i wehewehe ʻia e like me ke anawaena coherent (DCOH), e wehewehe ana i ka palena kiʻekiʻe o ka hoʻohuli ʻana o ka magnetization o ka ʻōnaehana ma o ka huli ʻana.ʻOiai aia kahi ʻokoʻa nui i ka nui o ke kino o nā ʻāpana (ʻo ka SFOA he 10 mau manawa nui ma mua o SFOC), ua mau a liʻiliʻi kēia mau waiwai, e hōʻike ana i ka hoʻololi ʻana o ka magnetization o nā ʻōnaehana āpau e like me ka mea a mākou e koi ai. ʻo ia ka ʻōnaehana domain hoʻokahi) 24 .I ka hopena, ʻoi aku ka liʻiliʻi o ka VACT ma mua o ka XRPD a me TEM analysis (VXRD a me VTEM ma ka Papa S3).No laila, hiki iā mākou ke hoʻoholo ʻaʻole hiki wale ke kaʻina hana hoʻololi ma o ka hoʻololi ʻana.E hoʻomaopopo i nā hopena i loaʻa ma ka hoʻohana ʻana i nā magnetometers like ʻole (Figure S4) hāʻawi i nā waiwai DCOH like loa.Ma kēiaʻano, he mea nui ka weheweheʻana i ke anawaena koʻikoʻi o kahi'āpana domain hoʻokahi (DC) i mea e hoʻoholo ai i ke kaʻina hana hoʻohuli kūpono loa.Wahi a kā mākou loiloi (e ʻike i nā mea hoʻohui), hiki iā mākou ke hoʻomaopopo i ka loaʻa ʻana o ka VACT e pili ana i kahi ʻano hoʻololi incoherent, no ka mea, mamao loa ka DC (~ 0.8 µm) mai ka DC (~ 0.8 µm) o kā mākou mau ʻāpana, ʻo ia hoʻi, ka ʻAʻole i loaʻa ke kākoʻo ikaika a loaʻa kahi hoʻonohonoho domain hoʻokahi.Hiki ke ho'ākāka 'ia kēia hopena ma o ka ho'okumu 'ia 'ana o ka domain interconnected25, 26. Mana'o mākou he ho'okahi crystallite e komo ana i loko o ka pilina pili, e ho'onui ana i nā mea pili ma muli o ka microstructure heterogeneous o kēia mau mea27,28.ʻOiai ʻoi aku ka maʻalahi o nā ʻano X-ray i ka microstructure maikaʻi o nā kāʻei kapu (microcrystals), hāʻawi nā ana hoʻomaha magnetic i nā hōʻike o nā hanana paʻakikī e hiki mai ana i nā SFO nanostructured.No laila, ma ka hoʻonui ʻana i ka nanometer nui o nā kīʻaha SFO, hiki ke pale i ka hoʻololi ʻana i ke kaʻina hana hoʻohuli multi-domain, a laila e mālama i ka coercivity kiʻekiʻe o kēia mau mea.
(a) ʻO ka pihi magnetization hilinaʻi manawa o SFOC i ana ʻia ma nā koina HREV ʻokoʻa ma hope o ka saturation ma-5 T a me 300 K (i hōʻike ʻia ma ka ʻaoʻao o ka ʻikepili hoʻokolohua) (ua hoʻohālikelike ʻia ka magnetization e like me ke kaumaha o ka hāpana);no ka akaka, Hōʻike ka inset i ka ʻikepili hoʻokolohua o 0.65 T kahua (ʻeleʻele pōʻai), nona ka mea kūpono loa (laina ʻulaʻula) (ua hoʻohālikelike ʻia ka magnetization i ka waiwai mua M0 = M (t0));(b) ʻo ka viscosity magnetic e pili ana (S) ʻo ia ka inverse o SFOC A hana o ke kahua (ʻo ka laina ke alakaʻi no ka maka);(c) kahi hoʻolālā mīkini hoʻāla me nā kikoʻī kikoʻī o ka lōʻihi kino/magnetic.
Ma ka ʻōlelo maʻamau, hiki ke hoʻohuli ʻia ka magnetization ma o nā kaʻina hana kūloko, e like me ka nucleation wall domain, propagation, a me ka pinning a unpinning.I ka hihia o nā ʻāpana ferrite domain hoʻokahi, ua hoʻopili ʻia ka mīkini hoʻāla i ka nucleation-mediated a ua hoʻoulu ʻia e ka hoʻololi magnetization ʻoi aku ka liʻiliʻi ma mua o ka nui o ka hoʻohuli ʻana o ka magnetic (e like me ka hōʻike ʻana ma ke Kiʻi 6c)29.
ʻO ke āpau ma waena o ka magnetism koʻikoʻi a me ke anawaena kino e hōʻike ana i ke ʻano incoherent he hanana concomitant o ka hoʻohuli ʻana i ka domain magnetic, ma muli paha o ka inhomogeneities waiwai a me ka ʻili ʻole o ka ʻili, e hoʻopili ʻia ke piʻi ka nui o ka ʻāpana 25, e hopena i kahi ʻae ʻana mai. kūlana magnetization like.
No laila, hiki iā mākou ke hoʻoholo i kēia ʻōnaehana, paʻakikī loa ke kaʻina hana hoʻohuli magnetization, a ʻo ka hoʻoikaika ʻana e hōʻemi i ka nui ma ka nanometer scale ke kuleana nui i ka pilina ma waena o ka microstructure o ka ferrite a me ka magnetism..
ʻO ka hoʻomaopopo ʻana i ka pilina paʻakikī ma waena o ke ʻano, ke ʻano a me ka magnetism ke kumu no ka hoʻolālā ʻana a me ka hoʻomohala ʻana i nā noi e hiki mai ana.Ua hoʻopaʻa ʻia ke ʻano anisotropic o nā nanocrystals i loaʻa i kā mākou ʻano synthesis ka hōʻike ʻikepili laina o ka XRPD i koho ʻia o SrFe12O19.Hoʻohui ʻia me ka ʻimi TEM, ua hōʻoia ʻia ke ʻano polycrystalline o kēia ʻāpana, a ua hōʻoia ʻia ʻo ka nui o ka SFO i ʻimi ʻia ma kēia hana ʻoi aku ka haʻahaʻa ma mua o ke anawaena kikowaena koʻikoʻi hoʻokahi, ʻoiai nā hōʻike o ka ulu ʻana o ka crystallite.Ma kēia kumu, manaʻo mākou i kahi kaʻina magnetization hiki ʻole ke hoʻololi ʻia e pili ana i ka hoʻokumu ʻana i kahi kikowaena pilina i haku ʻia me nā crystallites pili.Hōʻike kā mākou mau hualoaʻa i ka pilina pili ma waena o ka morphology particle, ka hana aniani a me ka nui crystallite e noho nei ma ka pae nanometer.Ke manaʻo nei kēia noiʻi e wehewehe i ke kaʻina hana magnetization reversal o nā mea magnetic nanostructured paʻakikī a hoʻoholo i ka hana o nā ʻano microstructure i ka hopena magnetic.
Hoʻopili ʻia nā laʻana me ka hoʻohana ʻana i ka waikawa citric ma ke ʻano he chelating agent/fuel e like me ka sol-gel spontaneous combustion method, i hōʻike ʻia ma Reference 6. Ua hoʻopaʻa ʻia nā kūlana synthesis no ka loaʻa ʻana o ʻekolu mau ʻano nui like ʻole (SFOA, SFOB, SFOC). loaʻa ma o nā lāʻau lapaʻau annealing kūpono i nā mahana like ʻole (1000, 900, a me 800°C, kēlā me kēia).Hōʻuluʻulu ka Papa S1 i nā waiwai magnetic a ʻike ʻia ua ʻano like lākou.Ua hoʻomākaukau ʻia ka nanocomposite SrFe12O19/CoFe2O4 40/60 w/w% ma ke ʻano like.
Ua ana ʻia ke ʻano ʻokoʻa me ka hoʻohana ʻana i ka radiation CuKα (λ = 1.5418 Å) ma ka diffractometer pauka Bruker D8, a ua hoʻonohonoho ʻia ka laulā ʻāpana ʻike i 0.2 mm.E hoʻohana i ka helu VANTEC no ka hōʻiliʻili ʻana i ka ʻikepili ma ka laulā 2θ o 10-140°.Ua mālama ʻia ka mahana ma ka hoʻopaʻa ʻana i ka ʻikepili ma 23 ± 1 °C.Ua ana ʻia ka noʻonoʻo e ka ʻenehana step-and-scan, a ʻo ka lōʻihi o ka lōʻihi o nā laʻana hoʻāʻo a pau he 0.013° (2theta);ʻo ka helu kiʻekiʻe loa o ke ana ʻana he-2.5 a me + 2.5° (2theta).No kēlā me kēia kiʻekiʻe, ua helu ʻia ka huina o 106 quanta, aʻo ka huelo ma kahi o 3000 quanta.Ua koho ʻia kekahi mau piko hoʻokolohua (i hoʻokaʻawale ʻia a i ʻole ʻāpana ʻāpana) no ka nānā ʻana i ka manawa like: (100), (110) a me (004), i loaʻa ma ka ʻaoʻao Bragg kokoke i ke kihi Bragg o ka laina hoʻopaʻa inoa SFO.Ua hoʻoponopono ʻia ka ikaika hoʻokolohua no ka Lorentz polarization factor, a ua hoʻoneʻe ʻia ke kāʻei kua me kahi hoʻololi laina i manaʻo ʻia.Ua hoʻohana ʻia ka NIST maʻamau LaB6 (NIST 660b) e calibrate i ka mea kani a me ka spectral broadening.E hoʻohana i ke ʻano deconvolution LWL (Louer-Weigel-Louboutin) 30,31 no ka loaʻa ʻana o nā laina diffraction maʻemaʻe.Hoʻokomo ʻia kēia ʻano hana i ka polokalamu hoʻopili profile PROFIT-software32.Mai ka hoʻokomo ʻana i ka ʻikepili ikaika i ana ʻia o ka hāpana a me ka maʻamau me ka hana pseudo Voigt, ua unuhi ʻia ka laina laina pololei f(x).Hoʻoholo ʻia ka hana puʻunaue nui G(L) mai f(x) ma ka hahai ʻana i ke kaʻina hana i hōʻike ʻia ma ka Hōʻike 23. No nā kikoʻī hou aku, e ʻoluʻolu e nānā i ka mea hoʻohui.Ma keʻano he hoʻohui i ka hōʻikeʻike laina laina, hoʻohanaʻia ka polokalamu FULLPROF e hana i ka Rietveld i kaʻikepili XRPD (hiki ke loaʻa nā kiko'ī ma Maltoni et al. 6).I ka pōkole, ma ka Rietveld model, ua wehewehe ʻia nā peaks diffraction e ka hana pseudo Voigt ʻo Thompson-Cox-Hastings i hoʻololi ʻia.Ua hana ʻia ka hoʻomaʻemaʻe ʻana o LeBail i ka ʻikepili ma ka maʻamau NIST LaB6 660b e hōʻike i ka hāʻawi ʻana o ka mea kani i ka hoʻonui kiʻekiʻe.E like me ka FWHM i helu ʻia (ka laula piha i ka hapalua o ka ikaika o ka piko), hiki ke hoʻohana ʻia ka hoohalike Debye-Scherrer no ka helu ʻana i ka nui awelika o ke kikowaena hoʻopuehu puʻupuʻu.
ʻO ka λ ka lōʻihi o ka hawewe kukuna X-ray, ʻo K ke kumu hoʻohālike (0.8-1.2, maʻamau like me 0.9), a ʻo θ ka huina Bragg.Pili kēia i: ka noʻonoʻo i koho ʻia, ka hoʻonohonoho kūpono o nā mokulele a me ke kumu holoʻokoʻa (10-90°).
Eia kekahi, ua hoʻohana ʻia kahi microscope Philips CM200 e hana ana ma 200 kV a i hoʻolako ʻia me kahi filament LaB6 no ka loiloi TEM no ka loaʻa ʻana o ka ʻike e pili ana i ka morphology particle a me ka hāʻawi ʻana i ka nui.
Hana ʻia ke ana hoʻomaha hoʻomaha e nā mea hana ʻelua: Physical Property Measurement System (PPMS) mai Quantum Design-Vibrating Sample Magnetometer (VSM), i lako me 9 T superconducting magnet, a me MicroSense Model 10 VSM me ka electromagnet.ʻO 2 T ke kahua, hoʻopiha ʻia ka hāpana i ke kula (μ0HMAX: -5 T a me 2 T, kēlā me kēia no kēlā me kēia mea kani), a laila hoʻohana ʻia ke kahua hoʻohuli (HREV) e lawe i ka hāpana i loko o ka wahi hoʻololi (kokoke i HC ), a laila ua hoʻopaʻa ʻia ka The magnetization decay ma ke ʻano he hana o ka manawa ma luna o 60 mau minuke.Hana ʻia ke ana ma 300 K. ʻIke ʻia ka nui o ka hoʻāla ʻana ma muli o kēlā mau ana i wehewehe ʻia i loko o ka mea hoʻohui.
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