The domain state of magnetite detected in sediments of Shira lake (Khakassia, Russia) was examined by means of magnetic hysteresis. Analysis of experimental data obtained on samples from diﬀerent parts of bottom sediment cores in terms of Day plots allowed us to conclude that magnetite particles are in the pseudo-single-domain state. This indicates respectively small size of magnetite particles (< 100 nm) and reveals their bacterial origin. Biogenic magnetite buried in the bottom sediments can indicate the climatic changes in the Shira lake level in the Late Holocen

Balaev, Dmitry A.

Rogozin, Denis Yu.

Semenov, Sergey V.

Shaykhutdinov, Kirill A.

Siberian Federal University Digital Repository

Journal of Siberian Federal University. Mathematics & Physics 2017, 10(2), 252–256УДК 538.9Day Plots of Bacterial Magnetite from Sediments of ShiraLake (Khakassia, Russia)Sergey V. SemenovDmitry A.BalaevKirensky Institute of Physics SB RASAkademgorodok, 50/38, Krasnoyarsk, 660036Siberian Federal UniversitySvobodny, 79, Krasnoyarsk, 660041RussiaKirill A. ShaykhutdinovKirensky Institute of Physics SB RASAkademgorodok, 50/38, Krasnoyarsk, 660036RussiaDenis Yu.RogozinInstitute of Biophysics SB RASAkademgorodok, 50/50, Krasnoyarsk, 660036Siberian Federal UniversitySvobodny, 79, Krasnoyarsk, 660041RussiaReceived 10.08.2016, received in revised form 10.11.2016, accepted 20.01.2017The domain state of magnetite detected in sediments of Shira lake (Khakassia, Russia) was examined bymeans of magnetic hysteresis. Analysis of experimental data obtained on samples from diﬀerent partsof bottom sediment cores in terms of Day plots allowed us to conclude that magnetite particles are inthe pseudo-single-domain state. This indicates respectively small size of magnetite particles (< 100 nm)and reveals their bacterial origin. Biogenic magnetite buried in the bottom sediments can indicate theclimatic changes in the Shira lake level in the Late Holocene.Keywords: nanoparticles, magnetic hysteresis, bacterial magnetite.DOI: 10.17516/1997-1397-2017-10-2-252-256.IntroductionOne of crucial factors determining magnetic hysteresis of submicron size particles is thetype of their domain state. Among the single-domain (SD) and multi-domain (MD) states theintermediate between SD and MD, so called pseudo-single-domain (PSD) state is distinguished.These domain states are conventionally elucidated in terms of Day plots [1]. In this report thedomain state of magnetite detected in sediments of Shira lake (Khakassia, Russia) was examinedby means of analysis of magnetization curve M(H) measurements. The aim was to confirm (or todisconfirm) the bacterial origin of magnetite in sediments of Shira lake obtained from previoussmp@iph.krasn.ruc Siberian Federal University. All rights reserved– 252 –Sergey V. Semenov, Dmitry A.Balaev, Kirill A. Shaykhutdinov, Denis Yu.Rogozin Day Plots of Bacterial . . .study [2]. In [2] the non-monotonic dependence of magnetite content on the depth of sedimentswas found to correlate with the lake level indicating that the most probable source of magnetiteis magnetosomes of magnetotactic halolimnetic bacteria.1. ExperimentalLake Shira (5430’ N, 9011’ E) is located in the Chebakovo-Balakhtinskaya depression of theMinusinsk trough, a steppe region of the Republic of Khakassia (Siberia, Russia) was describedin detail elsewhere [3]. The bottom sediments were sampled on May 31, 2011 in the central partof Lake Shira at 5430.546’ N and 9011.442’ E. The lake depth of the sampling area was 24m. The sampling was made with the use of an Ekman box bottom grab taking a bottom areaof 160x160 mm. The samples were cut from several parts of bottom sediment cores (obtainedin 2011) corresponded to diﬀerent depths (in mm) of sediments. Magnetic measurements wereperformed by using vibration sample magnetometer. A signal from the sample with a capsule wascorrected by the diamagnetic signal from the capsule; then, the magnetic moment was normalizedto the unit sample mass.2. Results and discussionThe Fig. 1 shows typical field dependence of magnetization M(H) for sediment sample. Hys-teresis of the M(H) dependence in the field range up to 2 kOe is seen. Another feature of theM(H) dependence is its linear behavior in the range of fields higher than 2 kOe. The slope ofthis linear dependence was found to decrease with increasing of temperature. The inset of Fig. 1shows the temperature dependence of magnetic moment M(T) of the sample measured in theexternal field of 1 kOe. There is a a kink on the M(T) dependence at temperature of 120 Kcorresponding to the Vervey transition of magnetite. The decrease of the magnetization withtemperature is due to additional paramagnetic contribution from Fe2+ and Fe3+ ions [2]. Thisparamagnetic (PM) contribution was taken into account and the ferrimagnetic (FM) contribution(from magnetite) was extracted from M(H) and M(T) data, see the Fig. 1.To build the Day plots a set of minor hysteresis curve with step by step increase of the maximalapplied field Hmax (up to Hmax corresponding to the major loop) were recorded. The valuesof remanence MR, saturation magnetization MS , coercivity HC , and HCR (HCR corresponds tothe Hmax value at which the remanence is 0.5 of the MR magnitude for the major loop) weredetermined from these data. The Fig. 2 shows major and minor hysteresis M(H) curves togetherwith typical example of determination of MR, MRS , HC , and HCR values. The experimental dataobtained on several samples from diﬀerent depths of sediments were plotted in the co-ordinatesMRS/MS , HCR/HC . According to [1] the SD, PSD, and MD states correspond to areas shownin the Fig. 3. As can be seen from this figure the experimental data obtained on samples fromvarious depths are located in the PSD region. This indicates respectively small size of magnetiteparticles (< 100 nm) [4] and reveals their bacterial origin.ConclusionsThus, the magnetic state of the magnetite particles buried in the sediments of the Shiralake is the pseudo-single-domain. This points out the small size (< 100 nm) of the magnetite– 253 –Sergey V. Semenov, Dmitry A.Balaev, Kirill A. Shaykhutdinov, Denis Yu.Rogozin Day Plots of Bacterial . . .Fig. 1. Typical results of magnetic measurements of a sediment at the depth of 65 mm togetherwith FM and PM contributionsFig. 2. Typical major and minor hysteresis magnetization curves of a sediment at the depth of65 mm– 254 –Sergey V. Semenov, Dmitry A.Balaev, Kirill A. Shaykhutdinov, Denis Yu.Rogozin Day Plots of Bacterial . . .Fig. 3. The Day plots for the studied samples from the sediments of various depthsparticles and supports the conclusion of Ref. [2] that the source of magnetite in the sedimentsis magnetosomes of magnetotactic halolimnetic bacteria. Therefore, biogenic magnetite buriedin the bottom sediments can indicate the climatic changes in the Shira lake level in the LateHolocene.The work was supported by Russian Foundation for Basic Research and Krasnoyarsk RegionalScientific Foundation, Grant no. 15-45-04272 and partially supported by the Council on grantsfrom the President of the Russian Federation for support of leading scientific schools (grant NSh-9249.2016.5)References[1] R.Day et al, Hysteresis properties of titanomagnetites: grain-size and compositional depen-dence, Physics of the Earth and Planetary Interiors, 13(1977), 260–267.[2] D.Yu.Rogozin, D.A.Balaev, S.V.Semenov, K.A.Shaikhutdinov, O.A.Bayukov, MagneticProperties of Bottom Sediments from Meromectic Shira Lake (Siberia, Russia), DokladyEarth Sciences, 469(2016), 819–823.[3] A.G.Degermendzhy, et al, Vertical stratification of physical, chemical and biological com-ponents in two saline lakes Shira and Shunet (South Siberia, Russia), Aquatic Ecology,44(2010), 619–632.[4] D.Sarkar et al, Domain controlled magnetic and electric properties of variable sized mag-netite nano-hollow spheres, J. Appl. Phys., 112(2012), 064318.– 255 –Sergey V. Semenov, Dmitry A.Balaev, Kirill A. Shaykhutdinov, Denis Yu.Rogozin Day Plots of Bacterial . . .Графики Дэя для бактериального магнетита из донныхотложений озера Шира (Хакасия, Россия)Сергей В.СемёновДмитрий А.БалаевИнститут физики им. Л.В.Киренского СО РАНАкадемгородок, 50/38, Красноярск, 660036РоссияКирилл А.ШайхутдиновИнститут физики им. Л.В.Киренского СО РАНАкадемгородок, 50/38, Красноярск, 660036Денис Ю.РогозинИнститут биофизики СО РАНАкадемгородок, 50/50, Красноярск, 660036РоссияИсследовано доменное состояние магнетита, обнаруженного в донных отложениях озера Шира(Хакасия, Россия). Из анализа экспериментальных данных по намагниченности образцов с разныхучастков керна донных отложений, а также на основе графиков Дэя сделан вывод, что части-цы магнетита находятся в псевдооднодоменном состоянии. Это указывает на малый размерчастиц магнетита (< 100 nm) и подтверждает их бактериальное происхождение. Биогенныймагнетит, содержащийся в донных отложениях, может служить индикатором климатиче-ских изменений в уровне озера Шира в позднем голоцене.Ключевые слова: наночастицы, магнитный гистерезис, бактериальный магнетит.– 256 –

Day Plots of Bacterial Magnetite from Sediments of Shira Lake (Khakassia, Russia)

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Day Plots of Bacterial Magnetite from Sediments of Shira Lake (Khakassia, Russia)

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